oots!" Gregor was beginning to panic. She'd been right here a minute ago. Hadn't she? Or had he been so busy thinking, he'd lost track of how much time had passed? "Boots!"

Where could she have gone? Into the trees? Out onto the street? What if someone had taken her? "Boots!"

There wasn't even anyone around to ask. The park had emptied out as dark had fallen. Struggling to stay calm, Gregor tried to follow the trail of footprints that she'd been making in the snow. But there were so many footprints! And he could barely see!

Suddenly he heard a dog barking nearby. Maybe it had found Boots, or at least its owner might have seen her. Gregor ran through the trees to a small clearing somewhat illuminated by a nearby light. A feisty little terrier was running in a circle around a stick, barking its head off. Intermittently it would grab the stick in its jaws, give it a good shake, and drop it on the ground. Then it would begin its frantic barking again.

A pretty woman, dressed in winter jogging clothes, appeared. "Petey! Petey! What are you doing?" She scooped up the dog and shook her head at Gregor as she walked off. "Sorry, he goes a little crazy sometimes."

But Gregor didn't respond. He was staring at the stick, or what he'd thought was a stick, that had been driving the dog wild. It was smooth and shiny and black. He picked it up and it bent in two. Not like a broken stick. But like a leg. An insect leg. From a giant roach...

His head whipped around the area. When they had returned from the Underland that summer, they had come up through a series of tunnels that led to Central Park. They had been near the street, just as he was now.

There, on the ground. That big slab of rock. It had been moved recently — he could tell by the marks in the snow — and then moved back into place. Something red was trapped under the edge of the rock. He pulled it out. It was Boots's mitten.

The giant roaches from the Underland had idolized Boots. They'd called her the princess and done some special ritual dance to honor her. And now they'd kidnapped her right out from under his nose.

"Boots...," he said softly. But he knew she couldn't hear him at this point.

He pulled out his cell phone. They couldn't afford a cell phone, but after three members of her family had mysteriously disappeared, his mother had insisted they get one, anyway. He dialed home. His dad answered.

"Dad? It's Gregor. Look, something happened. Something bad. I'm in Central Park, near that place where we came up this summer, and the roaches, you know, the giant ones? They were here and they took Boots. I wasn't watching her close enough, it's my fault and...I have to go back down!" Gregor knew he had to hurry.

"But...Gregor..." His dad's voice was full of confusion and fear. "You can't —"

"I have to, Dad. Or we might not ever see her again. You know how crazy the roaches are about her. Look, don't let Mom call the police this time. There's nothing they can do. If I'm not back right away, tell people we've got the flu or something, okay?"

"Listen, stay there. I'm coming with you. I'll be there as quick as I can," said his dad. Gregor could hear him panting as he tried to struggle to his feet.

"No, Dad! No, you'd never make it. You can't even walk down the block!" said Gregor.

"But I...but I can't let you..." He could hear his dad beginning to cry.

"Don't worry. I'll be okay. I mean, I've been down there before. But I got to go, Dad, or they'll get too far." Gregor puffed as he struggled to slide away the slab of rock.

"Gregor? You have any light?" asked his dad.

"No!" said Gregor. This was a real problem. "Wait, yes! Yes!" Mrs. Cormaci had given him a mini flashlight in case the lights ever went out when he was on the subway. He had clipped it to his key ring. "I've got a flashlight. Dad, I've got to go now."

"I know, son. Gregor...I love you." His dad's voice was shaking. "Be careful, okay?"

"I will be. Love you, too. I'll see you soon, okay?" said Gregor.

"See you soon," his dad whispered hoarsely.

And then Gregor lowered himself down into the hole. He stuck the phone in one pocket and pulled out his key ring from another. When he clicked on the little flashlight, he was surprised by the amount of light it produced. He slid the rock slab closed and started down a long, steep flight of steps.

As he got to the bottom he stopped and closed his eyes for a minute, trying to re-create in his head the path that had brought him here last summer. They had been flying then, on the back of a big black bat named Ares, who was his bond. In the Underland, a human and a bat could take a vow and swear always to protect each other no matter how desperate the situation. Then the two were called bonds.

Ares had flown Gregor, Boots, and his dad back from the Underland and left them at the foot of the stairs and headed off to the...right! Gregor was pretty sure it had been to the right, so he started running that way.

The tunnel was cold and dank and desolate. It had been made by people — regular people, not the violet-eyed, pale Underlanders he had met deep in the earth — but Gregor felt sure that it had been forgotten by New Yorkers long ago.

His flashlight beam caught a mouse, and it skittered away in terror. Light didn't come down here. People didn't come down here. What was be doing down here?

"I can't believe it," thought Gregor. "I can't believe I have to go back down - there! " Back into the strange dark land of giant roaches and spiders and, worst of all, rats! The thought of seeing one of those six-foot sneering, fanged creatures filled him with dread.

Boy, his mom was not going to like this.

Last summer, when they'd finally come home late one night, she'd freaked out. First her two missing kids show up with their missing dad, who can barely walk, and then they all sit down and tell her some bizarre story about a land miles under the earth.

Gregor could tell she didn't believe them at first. Well, who would? But it was Boots's chatter that she couldn't ignore.

"Beeg bugs, Mama! I like beeg bugs! We go ride!" Boots had said, happily bouncing on her mother's lap. "I ride bat. Ge-go ride bat."

"Did you see a rat, baby?" her mom said softly.

"Rat bad," Boots said with a frown. And Gregor remembered this was the exact phrase he had heard the roaches use to describe the rats. They were bad. Very bad. Well, most of them...

They'd told the story three times, under intense questioning from his mom. They'd showed her their strange Underland clothing woven by the huge spiders that lived there. Then there was his dad, white-haired, shaking, emaciated.

At dawn, she'd decided to believe them. At one minute after dawn, she was down in the laundry room nailing, screwing, gluing, doing everything she could to seal shut the grate they'd all fallen through. She and Gregor shoved a dryer closer to it. Not enough so it would draw a lot of attention. But enough so that no one could get back there and open it up.

Then she put the laundry room off-limits. No one was allowed down there, ever. So, once a week Gregor helped her haul the laundry three blocks to use a Laundromat.

But his mom hadn't thought about this entrance in Central Park. And neither had he. Until now.

The tunnel came to a fork. He hesitated a minute, and then headed off to the left, hoping it was the right direction. As he jogged along, the tunnel began to change. The bricks left off, and natural stone walls took over.

Gregor went down one last flight of steps. This one was carved out of natural stone. It looked really old. He guessed it must have been made by the Underlanders hundreds of years earlier, when they'd begun their descent to make a new world deep in the earth.

The tunnels began to twist and turn, and soon Gregor lost his bearings. What if he was just getting totally lost in some maze of tunnels while the roaches carried Boots off in a completely different direction? What if he'd taken a wrong turn back at the stairs...what if...no, there! His flashlight landed on a spot of red on the ground, and Gregor picked up Boots's second mitten. She could never hold on to them. Luckily.

As Gregor sprinted off, he began to notice a crunching sound under his feet. Shining the flashlight onto the floor, he realized it was covered with a variety of small insects scurrying down the tunnel as fast as they could.

As he stopped to investigate the situation, something skittered over his boot. A mouse. There were dozens running past him. And there by the wall — hadn't he just seen some kind of molelike animal go by? The whole floor was alive with creatures headed in Gregor's direction in a big, creepy stampede. They weren't trying to eat one another. They weren't fighting. They were just running, the way he had seen animals on the news one time running from a forest fire. They were afraid of something. But of what?

Gregor shot the beam of his flashlight behind him and there was his answer. About fifty yards away, galloping toward him, were two rats. The Underland kind.