'm as sure as I can be," Evans said solemnly.

"Where is she right now?" Carol asked. Kevin stopped on his way down the stairs, alarmed by the stricken look on her face, the dull inevitability in her voice.

"I don't know. I haven't seen her for hours."

"We need to find her. Get out on the streets and see if you can track her down. Ask who's seen her. But keep it off the radio, you understand?"

"I understand."

"Good work, Sam," Carol said, knowing nobody else would ever thank him for what he'd achieved. She ended the call. She wanted to curl up in a ball and weep, but that would have to wait for later.

"Guv?" Kevin said, his tone concerned. Carol knew his anxiety wasn't really for her, but she forgave him anyway.

"The Creeper," she said. "Sam's got an ID from one of the street girls."

Kevin's face lit up. "But that's great news."

"No, it's not," Carol said flatly. It was as if she couldn't bring herself to tell him. She turned away and began to run down the stairs. "Stacey," she shouted. "And you too, Kevin. With me, now."

Kevin caught up with her at the car, Stacey at his heels. "Who is it?" he demanded. "Who is it?"

Carol's face clenched momentarily in pain. "Jan Shields," she said.

Kevin recoiled as if he'd been struck in the face. He gave an incredulous little laugh. "It's a wind-up," he said. "Somebody with a score to settle."

"Sam says not," she said heavily. "I should have listened to Tony," she added, running a hand through her hair. "Can we get a move on, please, Kevin?"

Dazed, he unlocked the car and they piled in. "Stacey, call the station and get a home address for Jan Shields," Carol said over her shoulder. "Fuck, I should have listened to Tony."

"What? He said it was Jan Shields?" Kevin sounded incredulous.

"He said there was a cop behind this. I wouldn't believe him."

"Where am I going?" Kevin said as Carol slammed the noddy light back on the roof.

From the back seat, Stacey shouted the address. "It's on the Micklefield estate," she said.

"We've still only got one hooker's word for it," Kevin said as he carved a line through the traffic. "And it makes no sense."

Carol sighed as if she had the weight of the world on her shoulders. "Oh, it makes sense all right. It's the first thing that's made sense since this whole fucking business began."

Tony clicked another button, hoping it might provide some indication of where the webcam feed was coming from. He'd left the screen itself, unable to bear the sight of Paula's vulnerability. At least she was still alive. It was, he knew, time to call Carol. Stacey Chen was far better equipped for this task than he was.

He reached for his mobile. He'd barely got his hand out of his pocket when he heard a low voice behind him that chilled him to the bone.

"You're a burglar. I'm quite within my rights."

He froze and slowly turned. Jan Shields was inches from him, her weight balanced perfectly, a glittering blade held almost carelessly in her hand. Her eyes were cold and steady, her whole attitude one of carefully contained violence. "Drop the phone on the floor," she added.

He did as he was told. He didn't doubt for a moment that she would have had no hesitation in cutting him if he hadn't complied. "Might be a bit hard to argue reasonable force. I mean, everybody knows I'm a weed."

Her lip curled in contempt. "I don't think I'll ever have to make the argument. Because nobody knows you're here, do they?"

"Carol knows." He said it casually, trying to make it convincing.

She shook her head. "I don't think so. She does things by the book, does the lovely Carol. She would never let you come out to play by yourself. I rather think you're all mine, Dr. Hill."

She was so accustomed to dominating, he thought. The only way under her guard was to take the power from her. Which was fine in theory. His problem was that he was woefully short on leverage. "This isn't your style, Jan," he tried for starters.

For some reason, his words had amused her, "You think not?"

"It's way too hands-on. You like somebody else to do the dirty work."

She raised one eyebrow. "Are you suggesting I've got something to do with these murders?" she said, her cherub's face assuming a look of injured innocence.

"They're your murders, Jan. You should be proud of them. They're interesting pieces of work."

"That's as maybe. But they're nothing to do with me, Dr. Hill. Derek Tyler killed four women. And a retard called Carl Mackenzie did three more copycat murders before he topped himself in remorse only this afternoon. That's what the evidence shows."

Oh Christ, she's killed with her own hands. The knowledge hit Tony with the force of a lightning strike. He felt his own chances shrivel to ash. But still, he had to try. "Come on, Jan. There's no point in lying now. Carl Mackenzie hasn't done three murders. Paula Mclntyre is still very much alive."

"You obviously know more about it than I do. Maybe you're the person behind it all. Maybe you've set me up. Maybe you're the person who's been sending me all this sick stuff."

He shook his head, aiming for an air of disappointment. "That dog won't hunt. Carol Jordan knows me too well to fall for that."

"I can make it look that way. With you dead and the ends all tied up, who's going to listen to your favourite blonde? Everybody knows she's lost it. Face it, Dr. Hill, you're a busted flush."

Kevin turned into the Micklefield estate and slowed to a halt at the end of the street where Jan Shields lived. "What now?" he said. "It's a cul-de-sac. If she's looking out for us, she's going to see us the minute we turn into it."

"Your car's pretty nondescript. We could drive up and just turn into somebody's drive near her house. There's not much light, and it's not like we'd be doing anything suspicious."

Kevin drove slowly up the cul-de-sac. Almost at once, he spotted Jan's distinctive car. "Looks like she's at home," he said.

"Stick to the plan," Carol replied. "There, that one on the right a couple of doors down from hers. The house will shield us from her line of sight if we pull right up the drive."

"What now?" Kevin asked. "We could just front her up. Arrest her on suspicion and do a search."

Something was niggling at the corner of Carol's mind. "Does anyone know where Tony is?"

"He said he was going home to write his profile," Stacey reminded her.

Carol took out her phone and speed-dialled Tony's home number. It rang a few times then the machine kicked in. She waited for the beep, then said, "Tony, it's Carol. If you're there, pick up. It's urgent." She waited for half a minute, then cut off the call. She tried his mobile, but it rang out interminably without an answer. "Oh shit," she said, a terrible apprehension hitting her.

"There's no reason to suppose he's in there," Kevin said anxiously.

"Apart from that little pantomime with Jan's lost keys earlier." Carol felt the pieces sliding into place, the picture forming in her mind's eye.

"What little pantomime?"

"Jan mislaid her keys. And Tony stepped out of absent-minded professor role long enough to remind her she hadn't locked her car. How likely is that, on both counts? But I just didn't see it at the time." She swallowed hard. "He's in there, Kevin. In there with her."

"We don't know that," he said.

"We need to find out. Stay there," Carol ordered, opening the car door, ignoring the looks of dismay on her colleagues' faces. She walked to the corner of the building and sneaked a look round it. She was at a tangent to Jan's house. She could see part of the living room, which was empty. The front window upstairs was also brightly lit. Anyone watching from in there would be visible from where Carol was standing. Time to take a chance.

She sprinted along the front of the house, jumping a low hedge and crossing the garden of the house next door. That brought her to the edge of Jan's drive', alongside her car. A big window towards the rear of the gable end spilled light on to the paved blocks of the drive and splashed it up the side of the garage. She calculated that if she could make it to the far end of the window undetected, she could use the shelter of the garage to look into the window from far enough away not to be obvious to anyone inside.

She crouched down and circled behind the car, making it to the gable end and flattening herself against the wall. She edged up until she was almost level with the window, then crouched down and crept along below the sill for a few feet before straightening up. She was just outside the oblong of light. Taking a deep breath, she covered the distance to the rear of the garage in seconds.

Relying on the pool of shadow to obscure her, Carol turned and stood up. She had a clear line of angled vision into the dining room. She could see Jan from the waist up. And, slightly to one side of her, she could see the back of Tony's head. Her chest tightened. Why the fuck didn't you call me? As she watched, Jan's right hand came up into view in what looked from that distance to be a casual gesture.

But there was nothing casual about the knife that refracted light in a gleaming line that seemed to cut to Carol's very heart.

The insistent chirrup of Tony's mobile stopped as suddenly as it had begun. Jan nodded. "Good boy. You didn't even try to answer it."

"This is what you like, isn't it? The moment of power. Control. The world bent to your will."

She cocked her head. "If you say so."

"I know so. It was a beautiful idea. Working on mentally susceptible men, making them your tools. A double dose of power. You control them and they control the victim according to your script. I take my hat off to you. It can't have been easy, getting them word perfect."

She smiled. "I know what you're trying to do. And it isn't going to work. There's no point in playing for time when the cavalry don't know where you are."

He stood up. "I'm not playing for time."

"Sit down," she ordered him.

"I don't think so," he said. "You know there's no way out for you."

Her eyes narrowed. "I told you. I can make it look like you tried to set me up. I caught you in the act, we struggled, you died."

"Underestimating the opposition. It's the one mistake that brings people down more than any other."

She gave a derisory snort. "What's to underestimate? We both know where the power resides. I'm a cop. You? You're just a very strange little man who weir ds people out."

"No, no, you misunderstand me. I'm not your problem. I don't actually mind dying, you see. No, your problem is Carol Jordan. I told her what I suspected. OK, she laughed at me. But if anything happens to me, she'll come after you."

She looked scornful. "Carol Jordan doesn't scare me."

"That's what I mean about underestimating the opposition. She should scare you. Because, contrary to what you think about her, she's not afraid of getting her hands dirty. She won't be hiding behind some poor inadequate sod like Derek Tyler or Carl Mackenzie. She'll take you down, and she'll do it in the worst way."

"I'll take my chances."

He turned away. "I don't think so. You're too accustomed to making other people take them for you."

"Where do you think you're going?" she yelled, her control suddenly slipping.

He glanced back at her. "I'm tired of talking. You're history and I'm going home."

Galvanized into action, she lunged forward and grabbed his arm, spinning him towards her. Then the knife was in the air, gleaming between them, searching for flesh.

As soon as she saw the knife, Carol knew there was no time for anything other than action. She raced to the back door of the house, making a lunge for the door handle. To her surprise, it gave under her hand and she half-tumbled, half-ran into the kitchen. She saw a freeze-frame of Jan bearing down on Tony, the weapon hidden from her by their bodies. His mouth opened in a scream of pain. "Drop the knife," Carol yelled desperately at the top of her voice as she crossed the kitchen in a handful of strides.

At the sound of her cry, Jan hesitated long enough for Tony to stagger out of the arc of her knife. She glanced back at Carol, turned to flash a look of hatred at him before Carol launched herself across the last few feet between them.

Carol's momentum drove them both crashing to the floor in a struggling tangle of limbs. At first, Carol had no idea where the knife was and she scrabbled for purchase so she could pin down Jan's wrist.

"Let me go," Jan shouted. "You're hurting me."

"Drop the knife," Carol yelled back, her face inches from the other woman's.

"I dropped it already." The words came out almost as a scream. "Get off me." Her body bucked under Carol. Then suddenly Tony was on the floor beside them, pinning Jan's shoulders to the floor with his knees. Blood was streaming from one of his hands, and he clutched it to his chest.

"The knife's on the floor, Carol," he said.

Carol eased back, panting, her weight keeping Jan's lower body immobilized. "You're making a big mistake," Jan gasped.

"I don't think so," Carol said. "Jan Shields, I am arresting you on suspicion of conspiracy to commit murder .. ."

"You don't get it, do you?" Jan howled.

"Save it for the interview room. You do not have to say anything .. ."

"Carol, listen to me," Jan said, dragging all her resources together to give her voice the note of assured command. "I'm the victim here. You need to listen to me."

Don Merrick couldn't remember ever having been so cold in his life. He'd gone beyond shivering and into a kind of physical trance, his body numb and heavy. And still no sign of Nick Sanders.

He'd reached Achmelvich in the early evening, at the end of a single-track road that cut high above the slender finger of a sea loch. The occasional tree he'd passed had been bent double, a marker to indicate the force and direction of the prevailing wind.

It was hardly worth giving a name to, he thought. There was the youth hostel, closed for the winter, and a handful of low cottages hunched along a spine of rock that stretched out into the sea. Only one of the cottages was showing a light. He wondered if he should ask for directions, but figured it couldn't be that hard to find this Hermit's Castle.

He'd been wrong, of course. He'd spent the best part of an hour clambering over rocks in the wrong shoes, stumbling on loose stones, nearly tumbling headlong into the sea at one point. When he'd finally found it, he'd almost walked straight past it.

Exhausted, cold and bruised, he shone his torch over the tiny concrete structure. It was nestled in a gap in the rocks, a grey box scarcely seven feet high with a small chimney curved over the roof like a tail. There was a doorway but no door. It led to a narrow passage that curved round, apparently designed to keep out the wind and the rain. It gave on to a tiny cell, barely six feet across. Along one side was a concrete shelf the size and shape of a single bed. Opposite was an open hearth. And that was it. Nowhere to hide, nowhere to do anything much. He couldn't imagine spending a day there, never mind a year.

Merrick went back outside and shone his torch around. Nothing to do but wait. He'd give it till ten, he decided, then leave. If Nick Sanders arrived after that, he wouldn't be going anywhere before morning. If, of course, he was coming there at all.

A short distance beyond the hideaway, Merrick found a sheltered space in the rocks and hunkered down. He'd come across a petrol station earlier where he'd managed to buy a heavy rubber torch, some cans of Coke, a couple of packets of biscuits and some crisps. He'd also bought a hideous hand-knitted jumper which he'd hoped might protect him against the cold. It didn't seem to be helping much.

The sound of the sea crashing against the rocks was hypnotic. There were moments when he felt himself drifting into a doze, starting awake only because his body shifted and some part of him hit a different bit of rock. Thoughts of Lindy and his sons drifted in confusion around his head. They were why he was here. Somewhere in the deep recesses of his mind, he knew that a large part of the reason he was so determined to bring Tim and Guy's murderer to justice personally was that he felt it would be a kind of talisman, an act that would protect him from the prospect of losing his own boys. It almost assuaged the guilt he felt at abandoning Paula. But there were dozens of people out there working to bring Paula back, and nobody but him who cared enough about Tim and Guy to take a chance on this most slender of leads.

It was just after seven when he realized that there was another sound in the distance, a different note from the surge and crash of the sea. There was no doubt about it. It was a car. He shifted his position, trying to rub some life back into his frozen limbs. Either it was one of the cottage residents returning after a day doing who knew what in the back of this godforsaken beyond. Or it was Nick Sanders, going to ground where he thought he'd be safe.

The minutes passed, slow as hours. Then a glimmer of light rose behind the rocks. It grew brighter and clearer then, as it rounded an outcropping, became clearly identifiable as the steady beam of a big torch. Merrick ducked lower, though he knew there was little chance of anyone seeing him against the mass of black rock.

The beam swung round and illuminated the Hermit's Castle. Merrick could see nothing of the person behind the torch at first. But as the light disappeared inside the narrow passage, he could make out the shape of someone with a tall rucksack on his back. The height and bulk of the figure was, as far as he could make out, much the same as the description he'd read of Nick Sanders.

Merrick counted to sixty, then he stood up. It took a couple of minutes for his legs to feel capable of carrying him. He used the time to make sure his handcuffs were open and ready, his grip firm on his torch. Then he picked his way across the rocks in the darkness and stepped into the mouth of the passage. He walked as lightly as he could, picking up the sounds of someone moving around. The clank of tins. The rustle of plastic bags. Then he was in the chamber, looking down at the man crouched by the concrete shelf, illuminated by the light of a lantern-style torch. There was no doubt about it. This was the man whose photograph was pinned to the white board in the squad-room.

A slow smile of satisfaction spread across Merrick's face.

"Nick Sanders, I am arresting you on suspicion of murder," he said, enjoying every word.

He relaxed too soon. Sanders sprang up from his crouch, his momentum carrying him into Merrick and knocking him off his feet. Sanders tried to scramble over him and into the tunnel, but the space was too confined. Merrick lunged at his leg and caught him off balance. Sanders crashed into the wall and tripped up, falling backwards and cracking his head on the bed shelf.

He grunted once, then went slack. Merrick dragged himself upright and staggered across to Sanders. He was, to Merrick's regret, still breathing. He rolled Sanders over on to his side, not caring about the first rule of head injuries, seeing with satisfaction a swelling welt across the man's forehead. He glanced away as he went for his handcuffs. Suddenly Sanders uncoiled and sprang upwards, grabbing the heavy torch and swinging it savagely at Merrick's head. It caught him on the temple and at once, everything went red then black.

Carol stared at Jan Shields, incredulity on her face. "You're the victim here? Bullshit. Where's Paula?"

Jan's voice dropped into a warm, lower register. "I have no idea, Carol. Why don't you ask Dr. Hill? Like I said, I'm the victim here. I came home to find he'd made an illegal entry into my home. I found him typing something into my laptop. I grabbed a kitchen knife to defend myself against an intruder. I have no idea how long he has been here or what he might have planted."

"Nice try, Jan," Tony said, his voice strained. "Carol, there's a webcam feed. She's got it saved in her favourites. It's Paula. She's still alive."

"Does it say where she is?"

He shook his head. "Maybe Stacey can find something?"

Jan continued as if neither of them had spoken. "Like I said,

Carol, I found him in my home. I have no idea what he's talking about."

"Shut up," Carol said savagely. She shifted her position so she could reach her phone. She dialled Kevin's number. "Kevin, get up here now. Back door. Bring Stacey with you. Call for an ambulance, a SOCO team and uniformed back-up, please."

"You're going to look very foolish, Carol," Jan said, a pitying smile on her lips. "A well-respected police officer with commendations for bravery and experience of working with the FBI defends herself against an intruder in her home, an intruder intent on framing her for murder purely to protect the failing reputation of the woman he loves .. . That'll play beautifully in court, don't you think?"

Carol wished she could cover her ears and shut out the insidious poison coming from Jan Shields' mouth. "Like I said, save it for the interview room. I hope you've got something put aside for a rainy day. Bronwen Scott doesn't come cheap."

Jan chuckled. "Oh, I think I can afford a few hours of her time. That's all it'll take before Mr. Brandon realizes what a trumped-up mess of lies there is against me. And who's behind it."

Carol was spared listening to any more by the hasty arrival of Kevin and Stacey. She summoned them with a jerk of her head. "Cuff her and caution her, Kevin. I only got as far as "suspicion of conspiracy to commit murder". You might want to throw assault in for good measure. Tony, you can move away now," she said. She waited till he was clear and Jan was flanked by the other two before she rolled off Jan's legs and got to her feet.

"I'm sorry you're being forced to take part in this charade, guys," Jan said apologetically. "I keep telling Carol I'm the victim here, but she's got her own reasons for preferring to believe Tony, hasn't she?" She smirked at Carol as she spoke.

"Get her out of my sight," Carol said, crossing to Tony. "As soon as we get some uniforms here, I want her taken back to

HQ and banged up till I'm ready to talk to her." She took in his pallor and pulled a dining chair across for him. He slumped on the chair, holding his hand against his blood-soaked sweater. "How bad is it?" she asked.

"It hurts like hell. Won't stop bleeding." Beads of sweat formed on his forehead. Carol hurried through to the kitchen and grabbed a couple of dishtowels from their hooks. She folded them into pads and made him press them against the long slash that transversed his hand.

After a couple of minutes that felt much longer, flashing blue lights washed across the front window. "That's the ambulance," Carol said. "Come on, let's get you on your feet."

By the time the paramedics had loaded Tony into the ambulance, Kevin was escorting Jan into the back seat of a police car. Stacey was about to climb in with them when Carol called her name. "I need you back here," she said. Stacey followed her into the house. "There's a laptop picking up a webcam feed with live pictures of Paula. I need you to find out whatever you can, Stacey."

The younger woman nodded. "I'd be better off taking it back to the station," she said. "That way I have access to all my diagnostics."

"Fine. Just do it as fast as you can. Paula's still alive. It's obvious Jan's not going to give her up, so we need to do whatever it takes to find her before that changes," Carol said bleakly. She watched Stacey packing up the laptop, thoughts tumbling over each other in her head. She couldn't remember the last time she'd ever faced so complicated an end game It should have scared her, but instead it exhilarated her. She was definitely herself again. "Oh, and Stacey when you get back, can you call Don Merrick on his mobile and tell him I need him here. I'm going to the hospital to take a statement from Tony. I want Don to run the search here."

Fifteen minutes later, she was addressing a mixed team of SO COs and detectives. "We need to find where Paula is. There must be something a rent book, a utility bill, something. You have to be fast, but you also have to be unimpeachable. I don't have to tell you how vital this search is. Do what you need to do. Take up the carpets, shred the cushions if you have to. I don't care if you leave the place looking like a war zone, find Paula for me."

She turned away and spoke to the senior officer at the scene. "I'm going to the hospital to take a statement from Dr. Hill before I interview Shields. As soon as you get anything, call me. I'll have my phone switched on. To hell with their bloody heart monitors." She stopped on the threshold and gave the team a last level stare. "I know I can rely on all of you. And so does Paula."

Tony sat on the edge of the examination couch, a polystyrene cup of some indeterminate brownish liquid in his left hand. He'd waited less than ten minutes to be seen by the medical staff at Bradfield Cross A&E. Something to do with the amount of blood on his sweater, he suspected. Since then he'd been given a local anaesthetic, eight stitches and a cautious opinion that he probably hadn't done any permanent damage to his hand.

The curtains surrounding his cubicle moved and Carol's familiar face appeared in the gap. "Hi," she said. She slipped inside, closing the curtains behind her. "How are you doing?"

"I'll live," he said.

Carol hitched herself up on the bed beside him. "I need to take a statement from you."

He gave a tired, sad smile. "What do you need to know?"

"I need to know what happened between you and Jan. The earlier stuff how you got there, what the hell you thought you were playing at that can wait for later. But I want to know how it went down."

"I couldn't think of a way to make you believe me other than hard evidence," he said. "My failure." He sipped from the cup. Tea, he thought, though he wouldn't have been willing to wager anything he cared about on it. "Inside a file case that was hidden in her wardrobe, I found a bunch of photos and some DVD-ROMs. Photos of the victims before they were discovered. Photos presumably taken by Carl Mackenzie."

"You know about Carl?"

He nodded. "Jan told me the bare bones." He continued with the story, up to the point where he had turned to walk away.

"She came after me," he said. "I thought she would. I wanted to make her feel powerless, to lose control. That was my only chance of finding a chink in her armour that might have got me out of there alive." He smiled. "And that's when you arrived."

"She didn't actually confess?"

He shook his head. "No. Sorry. She was already practising the line she used on you."

"Never mind," Carol said. "We'll nail her."

"Paula?" Tony asked.

"We're looking. We'll find her." He could see the restored confidence in her face and hear it in her voice.

In spite of his concerns for Paula, part of Tony rejoiced.

Nick Sanders kicked the lifeless body at his feet. Bastard plod had screwed everything. He'd got it all planned. He was going to lay low for a week or two, until the hue and cry had died down and he'd had time to grow a beard. Then he was going to take the ferry across to Larne, drive down into Eire and disappear. It had all gone up in smoke now, thanks to this interfering copper. He'd have to hole up in some mountain bothy near the snow line, unable to risk venturing into populated areas. A child murderer would be off the front pages in a week by Sanders' reckoning, but a cop killer would be Public Enemy No.l until he was caught. Sanders had no intention of allowing that to happen.

He repacked his rucksack, wiped the blood from the torch on Don Merrick's sweater, then set off back across the rocky outcropping to the place where he'd left the car. It was near the end of the narrow tarmacked track that led down into the hamlet of Achmelvich, tucked away between the last cottage and the rocky headland. The low cloud robbed the landscape of light, and Sanders had to use his torch to prevent himself breaking a leg on the jagged rocks that lay between him and safety.

Eventually he emerged on the narrow path between the boulders, his breath white in the chill air, a thin film of sweat on his back. He broke into a shambling trot. He was only feet away from his car when a set of headlights on full beam snapped on and blinded him, silhouetting his tall frame against the uneven skyline.

A strong Highland voice rang out across the short distance between them. "Police. We'd like a word, sir."

Sanders didn't pause. He took to his heels, running back down the path towards the sea. He heard the sound of heavy feet behind him and panicked. He veered from the path and started scrambling over the boulders. He'd barely gone a dozen yards when a pair of powerful torch beams started playing over the rocks around him, pinning him down after a few seconds. He carried on gamely, but his pursuers had the advantage of being fresh and being able to see where they were going.

It was over in minutes. Two burly officers hauled Sanders to his feet, handcuffed him and half-dragged, half-carried him back to the path and to their waiting car. "What's this all about?" Sanders blustered as they went.

"You tell us, sir. Innocent people don't normally run away from the police," the older of the two officers said.