STOOD IN THE SHADOWS INSIDE THE FORT’S GATEWAY, HALF-HIDDEN behind the stone arch, and I watched as the large catamaran slid up to the dock and tied off. Many times in my sad short life I have waited in ambush and cuddled my wicked thoughts, but this was different. This was no deliciously private rendezvous on a carefully chosen night of silvery moonlight. This was a public execution in a crowd of strangers, a perversion forced on me by necessity, and it seemed like I was doing everything for the very first time. I felt stiff, clumsy, amateurish. I did not hear the sweet wing-rustle and whisper of encouragement from the Dark Passenger, and I did not hear the music of the Dance Macabre, and there was no delicious cool rush of power and certainty flowing out through my fingertips. My mouth was dry and my still-swollen hands were sweaty and I could hear my heart pounding rapidly in my ears and this was not wonderful wicked me lying in wait in complete control, not at all, and it made me fidgety and unhappy in a way that was almost painful.

But there was no choice, no way out, no direction but forward, and so I waited and watched as the ferry’s steel ramp slammed down onto the dock, and the crowd of gawkers surged off the boat and onto Dry Tortugas National Park, home of Fort Jefferson and Dexter’s Last Stand.

There were about sixty people on the boat, and most of them had come down the ramp and begun to amble around the outside of the fort before I saw Astor’s unmistakable blond head through a gap in the parade. A moment later the crowd parted again and there they were, all three of them. Cody and Astor held hands and Crowley walked very close behind them, herding them forward off the dock and onto the brick path toward the fort.

I tensed and slid deeper into the shadow of the stone gate. I flexed my fingers. They felt cramped and stupid, incapable of anything but knotting up. I made and unmade a fist several times, and when my hands felt as lively as they were going to get I reached into my pocket and took out my chunk of brick. It didn’t make me feel much better.

I waited. My throat was so dry that swallowing hurt, but I swallowed anyway and took a deep breath and tried to force icy calm into my veins. It didn’t work. My hands were shaky and the brick felt slippery in my grip. I took half a peek around the stone arch and for a few frozen seconds I didn’t see them anywhere. I eased out of the shadows a little more; there they were, standing stupidly in front of the sign, staring around them. I could see Astor’s mouth moving in what was clearly a tirade of irritation, and Cody’s small face was set in a scowl. Crowley had a duffel bag slung over one shoulder, and he wore an idiotic mask of pleasant anticipation, as if he really was on an enchanted holiday with two wonderful children.

But they didn’t move away from the sign. I wondered what Crowley had told them to keep them docile. It must have been good. They had no reason to distrust him if he had a plausible enough lie, but these were not ordinary, well-behaved children. Behind their pleasant and youthful features, throbbing inside their delightful tousled heads, dark and wicked flowers were blooming. Crowley could not possibly suspect it, but these were Dexters-in-Training, and they were, in every sense of the word, little Monsters. I felt a surge of affection for the two of them.

A clump of tourists stomped onto the drawbridge and came between me and Crowley. I stepped all the way back inside and pretended to be examining the stonework, but they didn’t even see me as they sauntered on through the gateway, chattering in Spanish and vanishing out the far side into the interior of the fort. When they were out of sight I eased my head around the arch and peeked out at the sign again.

They were gone.

Panic ripped through me and for a moment I couldn’t think anything at all. I just stared at the spot where they had been and squeezed my brick until my fingers hurt. Where could they be? And if they had to go somewhere, why weren’t they at least strolling over the drawbridge and into my ambush?

I leaned out farther and looked left; I saw nothing. I came a full step out of the archway and looked right—there they were, sauntering away on the sandy path to the far side of the island, toward the campground and away from my trap. Irritation boiled up inside me; what pointless stupidity were they performing? Why wasn’t Crowley bringing his fat head into the gateway and under my brick like he was supposed to do?

I watched as they ambled by a line of picnic tables and then past a clump of stunted trees that grew just before the beach, and then they were hidden by the branches and I couldn’t see them anymore.

I heard a hissing sound and realized it was me, blowing angry breath out between my teeth, and that was even more annoying. If that was the best I could do, I might as well go home now. I pried my fingers open and put the brick chunk back in my pocket, and, thinking very dark thoughts, I stepped into the sunlight and followed.

A family of five sat at one of the picnic tables. They were eating lunch, and they looked so happy I wanted to use the brick to bash in their heads. But I left them to their sandwiches and stalked down the path to the back side of the grove of scrub trees.

I paused for a moment, uncertain. The foliage screened me from Crowley, but it also hid him from me. He could very well be lurking just beyond the branches, watching his back trail for any Dexters that might be sniffing along behind him. Elementary predator’s caution would tell him to be sure no one was following. So, deciding that safe was very much better than sorry, I moved to my left, skirting along the back side of the tree line through even more picnic tables and ducking under a clothesline until I came to a break in the trees. I moved carefully around one last picnic table and into scrub. I pushed through the sand and the branches and stopped behind the last tree and slowly parted the leaves with my hand.

I should have seen them to my right, no more than thirty feet away. I didn’t. I pushed the branches farther apart, and there they were, standing stupidly on the sand and staring at the swimming area. If I slipped carefully back through the trees and came out behind them— But no. Crowley put one hand on each small shoulder and urged them back the way they had come, and the little trio slowly turned and trudged back into the scrub trees and headed toward the dock. It was obvious that he was scouting, making sure everything was just the way he wanted it to be, before he went to his special place to wait for me, the place where he would surprise me.

But, of course, I was already here, and I was going to surprise him first, if I could just stay close behind and watch for my chance—but how? There was very little cover between the trees and the dock, no more than one white metal building close to where the ferries tied up. Other than that, nothing but the fort, the water, and the thin sandy path leading around the tall redbrick walls. If I stepped out from the trees and followed I would be extremely visible. But I couldn’t let them just ramble away.

I looked in front of me on the beach. There were about half a dozen towels thrown around, with flip-flops and beach bags stacked beside them. The nearest towel was bright orange, and right beyond it there was a big white one. The towels’ owners were apparently all in the water.

At the far end of the beach, a large middle-aged woman sat in a fold-up canvas chair, watching a group of very loud children splashing around in the shallows. No one else was in sight, except for the people swimming farther out, toward the buoys marking the edge of the swimming area. I looked right again, and saw that Crowley and the kids were still strolling away around the fort.

A small idea popped into my head, and before I could think about how lame it was, I acted. Looking as casual as possible, I stepped out onto the beach, grabbed the white towel, and then strolled back into the cover of the trees. I took off my shirt and tied it around my waist, and then I draped the towel over my head like a bedouin headdress, clutching my half brick in one corner of the towel. I left the trees and walked through the picnic area. Look at me; I have been swimming and I have wet hair which I am now drying, and I am perfectly normal and not Dexter at all.

They were walking toward the far side of the fort now, past the dock and onto the sandy access road, and I followed. Suddenly, Cody stopped and turned around. He looked back toward the dock, then turned and looked at the fort, and then he frowned. I could see his lips move briefly, and he pointed at the drawbridge. Crowley shook his head and once more put a hand on his shoulder to urge him on, but Cody jerked away and pointed stubbornly at the drawbridge. Crowley shook his head and reached for Cody, who jumped away from him, and Astor stepped in between them and started talking.

I took advantage of their halt to get closer. I had no clear idea of how I was going to do this, but if I could get within half a brick length of Crowley I was ready to cave in his head and take my chances. Closer—and when I was only ten feet away I distinctly heard Astor say that this was all a bunch of bullcrap, and where was Dexter anyway? I raised my hands up and began to towel my head vigorously. I was actually within four big steps of them when Astor broke off her tirade, stared right at me, and said, “Dexter! You’re really here!”

I froze in place: stupid, I know, but I really was not my abnormal self. Crowley didn’t have that problem, and he wasted no time trying to see under the towel to confirm my identity. He dropped his duffel bag, yanked Astor off her feet, tucked her under one arm, and ran for the dock. She immediately began to wiggle frantically and yell at the top of her lungs, but without even slowing, Crowley punched her on the side of the head, hard, and she went limp.

I dropped the towel and jumped after them, paused for one second, and looked at Cody. “Go inside the fort,” I said. “Find the park rangers and tell them you’re lost.” And without waiting to see whether he would obey, I turned and sprinted after Crowley.

He had a good head start, but he was slower because he was carrying Astor, and I was closing fast when he pounded out to the end of the dock. A forty-five-foot sportfishing boat was backing in to tie up, and Crowley jumped onto the deck, where a woman in a bikini stood gaping at him and clutching the stern line. Crowley shoved her hard, and she went backward into the water, still holding the rope. An elderly man on the flybridge yelled, “Hey!” in a hoarse voice as Crowley dropped Astor to the deck. She slid up against a cooler and lay motionless, and Crowley lunged up the ladder to the flybridge. The old man yelled, “Help!” in a strangled self-conscious way, and then Crowley punched him in the gut and took the controls. The old man bent over and fell to his knees and the boat began to move away from the dock.

I was almost close enough to leap onto the deck when Crowley shoved the throttle forward and twirled the wheel hard over. The boat spun sluggishly around and began to move out toward the channel. And for once in this whole miserable adventure I did not hesitate or pause to think and bemoan. I ran the last few feet as fast as I could, and I jumped.

It was a good jump, very athletic, a nice arc to it and a near-perfect trajectory, and it was just good enough to splash me into the water three feet behind the boat. I went under and floundered to the surface again, just in time to see the boat start to accelerate. The prop wash boiled back at me, pushing me away and filling my mouth with water. And as I swallowed water and tried without hope to swim through the wake and grab the boat, something thumped me hard in the back and shoved me underwater again.

I had a horrible moment of panic as I remembered what the pilot had said about the Channel Hog, the largest hammerhead shark known to man—but the thing that had hit me felt too smooth to be a shark. I grabbed on to it and felt it pull me to the surface, and as I sucked in a breath and blinked the water out of my eyes I saw that I was holding a human leg. Even better, it was still attached to somebody—the bikinied woman Crowley had dumped into the water, and she was grimly clutching the stern line and dragging along behind the boat.

The boat began to pick up speed, and the wake foamed up around us, making it nearly impossible to see, and difficult to hold on. Very shortly I was sure it would be too much for the woman whose leg I was holding. She would let go, and then Crowley would be gone, taking Astor and all my hopes with him, probably for good this time. I could not let that happen.

And so, throwing caution and good manners to the wind, I grabbed higher up. My fingers clamped on to the band of fabric at the woman’s waist and I pulled myself forward—and suddenly I was sliding backward again as the bikini bottom shimmied off and down her legs, taking me with it.

I grabbed again, this time clamping on to her knee and then reaching up around her waist with both hands, and pulled upward until I got a hand on her shoulder. And just as I got one hand on the rope, the woman finally let go. Her body bumped against me, hard, and she scrabbled for a grip along the whole length of my body. For a moment I didn’t think I could hold on. But then she whirled away in the foamy white wake and I got my other hand on the rope and began to work my way toward the boat.

Slowly, hand over hand, fighting the turbulence every inch of the way, I jerked closer to the transom. I could see it clearly, tantalizingly close, bright blue letters spelling out its name and home port: REEL FUN, ST. JAMES CITY. And finally, after what seemed like hours but was probably no more than a minute or two, I got close enough to grab on to the boat’s dive platform, a narrow wooden shelf jutting out from the transom, and I clambered onto it, shoulders aching, breathing hard.

I flexed my hands; they were stiff and knotted up—and why not? After all they had been through the last few days I should have been grateful that they had not withered and fallen off. But they would have to perform one last good deed, and so I sent them ahead of me up the chrome ladder and I climbed into the cockpit of the boat.

I could just see Crowley’s head and shoulders above me; he stood on the flybridge, ten feet higher than the cockpit, looking forward and steering the boat out into the channel. Good—he didn’t see me, had no idea I was on board, and hopefully he wouldn’t until it was too late.

I hurried across the deck. The old man lay to one side, cradling his forearm and moaning softly. Crowley had clearly dumped him off the bridge and he had probably broken his arm in the fall. Very sad, but it didn’t really matter to me. I stepped past him to the ladder that led up to the flybridge. Astor lay at its foot, crumpled into a small untidy heap next to a cooler. The lid had bumped open, revealing ice and cans of beer and soda. I bent down beside Astor and felt for a pulse in her neck; it was there, steady and strong, and as I put a hand on her face she frowned and made soft and grumpy sounds. She would probably be all right, but there was nothing I could do for her right now.

I left her there and slithered up the ladder, pausing when my head came up just over the top step. I was looking at the back of Crowley’s legs. They looked spry, surprisingly muscular for someone I had thought of as doughy. I had misjudged him every step of the way, underestimated what he was capable of doing, and it made me hesitate now as a very un-Dexter thought came over me.

What if I couldn’t do this? What if I really had met my match, and he was just too much for me to handle? What if this was it, and the Dexter Show was about to end?

It was a truly horrible moment, and it got even worse when I realized what it was—real live human uncertainty. I really had fallen low. I’d never before doubted myself or my ability to perform routine executions, and this was a terrible time to start.

I closed my eyes for just a second, reaching out for the Passenger in a way I never had before, pleading for one last charge of the Dark Brigade. I felt it grumble, sigh, and rustle its wings—not really encouraging, but it would have to do. I opened my eyes and climbed quickly and quietly the rest of the way up the ladder onto the flybridge.

Crowley stood with one hand on the wheel, guiding the boat through the channel and away from the fort, and I hit him with my whole body as hard as I could. He slammed forward into the controls, bumping the throttle. The boat lurched forward, coming to top speed as I put my arm around Crowley’s throat and choked him with all my strength.

But he really was stronger than he looked. He dug his fingers into my forearm and pivoted, lifting me off the floor and bashing me into the side of the cockpit. My head bounced off the console; I saw stars, and Crowley slipped out of my grip.

Before I could throw off the dizziness he was on me, thumping me in the stomach, and although it took my breath away, at least it cleared my head, and I dropped to one knee and then punched sideways, connecting solidly with his kneecap. He said, “Oog,” very distinctly, and threw an elbow at my head that would have decapitated me if it had landed. But I ducked under it and scrambled to the other side of the bridge, jumping to my feet and turning shakily to face Crowley.

He straightened and faced me and we stood for a strange frozen instant, looking at each other. Then he took a step forward, feinted with his right hand, and, as I dodged, reached out with his left and yanked the boat’s throttle all the way back. The boat staggered to a stop, and I staggered with it, hitting the console with my hip and tipping toward the windscreen, struggling to regain my balance.

Crowley didn’t need to struggle; he had been braced for the sudden stop, and he was on me before I could recover. He hammered a knee into my midsection, and then he put both his hands on my throat and began to squeeze. Things quickly began to grow dim around me, and everything started to slow down.

So this was how it ended. Strangled by a Cub Scout leader—and not even the leader, merely an assistant. There didn’t seem to be a whole lot of glory in it. I got my hands onto Crowley’s wrists, but things were fading around me and it was getting very hard to stay interested.

And look there—I was already hallucinating houris in Paradise. Or was that really Astor coming up the ladder? It was her, and she was holding a can of soda from the cooler in the cockpit. Very thoughtful—my throat was hurting, and she had brought me a cool drink. It was unlike her to be so considerate—but now she was shaking the can as hard as she could. That was more like it. She was going to prank me with a spray of soda. A last sticky bath before dying.

But Astor stepped quickly around to Crowley’s side and pointed the can at his face. She screeched, “Hey, asshole!” And when Crowley turned to face her she pulled the tab. There was a very satisfying explosion and a great brown gout of soda shot out, right into Crowley’s eyes. Then she threw the can as hard as she could. It hit him squarely in the nose, and without a pause Astor stepped in and kicked him in the crotch.

Crowley staggered sideways under this unexpected onslaught, grunting with pain and taking one hand from my throat to wipe at his eyes, and as the pressure on my throat let up, a small trickle of light seeped back into my brain. I put both hands on the fingers remaining on my throat and I pried up hard. I heard one finger snap, and Crowley made a weird gargling noise and let go of me. Astor kicked his crotch again, and he took a drunken half step away from her and slouched over the railing.

And I, never one to waste an opportunity, hurtled forward and put my shoulder into him. He went right over, and there was an ugly thud-splash as he hit the gunwale below us and then flopped into the water.

I looked over the side. Crowley was bobbing in the water facedown, drifting slowly past us as the boat moved forward at idle speed.

Astor stood beside me, looking at Crowley as he bobbed away into our wake. “Asshole,” she said again. Then she gave me a wonderfully fake smile and said sweetly, “Is it okay to use that word, Dexter?”

I put an arm around her shoulders. “This time,” I said, “I think it’s okay.”

But she stiffened and lifted her arm to point. “He’s moving,” she said, and I turned to look.

Crowley had raised his head up out of the water. He was coughing, and there was a trickle of blood running down his face, but he paddled feebly away across the channel toward a nearby sandbar. He was still alive—after Astor and I beat him, kicked him, broke his hand, flung him from the bridge, drowned him, and even sprayed him with soda, he was still alive. I wondered if he was related to Rasputin.

I took the wheel of the boat and spun us around to point back to where Crowley was dog-paddling steadily toward safety and escape.

“Think you can drive this thing?” I asked Astor.

She gave me a look that very clearly said, Duh. “Totally,” she said.

“Take the wheel,” I told her. “Steer real close to him, slow and steady, and don’t run into the sandbar.”

“Like I would,” she said. She took the wheel from me and I hurried down the ladder.

In the cockpit the old man had straightened up into a sitting position, and his moaning had gotten louder. Clearly he would be no help at all. More interesting, however, was that there was a boat hook beside him in a set of clamps. I pried it out and hefted it: about ten feet long, with a heavy metal tip. Just the thing. I could smack Crowley in the temple with the tip, then hook his shirt with it and hold his head under for a minute or two, and that really should be an end to it.

I stepped over to the railing. He was in the water right ahead of us, thirty feet away, and as I raised the boat hook in preparation, the boat’s motors suddenly roared up the scale and we surged forward. I stumbled back and grabbed at the transom, regaining my balance just in time to hear something thump against the hull. The engines wound back down to idle and I looked up at Astor on the bridge. She was smiling, a real smile this time, and looking back into our wake.

“Got him,” she said.

I went back to the transom and looked. For a moment there was no sign of Crowley, and I could not see under the water in the foam of our wake. Then there was a slow, heavy swirl under the surface.… Was it possible? Was he still alive?

And with breathtaking speed and violence, Crowley’s head and shoulders broke the surface. His mouth was stretched into an enormous expression of unbelievable pain and surprise as he rocketed upward until the top half of his body was all the way out of the water. But there was an alien shape clamped around his middle and thrusting him upward, a colossal gray thing that seemed to be all teeth and malice, and it shook him with incredible force: once, twice, and then Crowley simply fell over from the waist, sliced neatly in two, and the top half of his body sank from sight and the gigantic gray thing swirled after him into the deep, leaving nothing but a small red whirlpool and the memory of unbelievably savage power.

It had all happened so fast that I couldn’t be sure I had really seen it. But the image of that great gray monster was burned into my brain as if it had been etched there with acid, and the foam in our wake had a faint pink tint to it now. It had happened, and Crowley was gone.

“What was that?” Astor said.

“That,” I said, “was the Channel Hog.”

“Sweeeet,” she said, drawing out the word. “Totally. Flippin’.!!!Sweeeeeeet.”