"You're sure?"

"Have to."

"Okay," he said uneasily. Then he continued, "Now, sounds don't work well underwater – hard to tell where they're coming from – but if you're in trouble bang on your tank with the knife and we'll search for you." He held up her SPG – submersible pressure gauge – which showed how much air was in her tank. "You've got three thousand pounds of air. You'll burn it fast because you're going to be pumped up on adrenaline. We leave the bottom with five hundred. No less than that. That's an iron-clad rule. No exceptions. We come up slow – no faster than the bubbles from our regulator and we pause for three minutes fifteen feet down."

Otherwise, Sachs knew, there was a risk of decompression sickness – the bends.

"Oh, and what's the most important rule in scuba?"

Sachs remembered it from her course years ago. "Don't ever hold your breath underwater."

"Good. Why?"

"Otherwise your lungs could explode."

Then they started her air and she pulled on her fins then mask, gripped the regulator fiercely in her teeth. The dive chief gave the other "okay" sign – middle finger and thumb in a circle – and she responded the same way. She pumped some air into her BCD to allow her to float on the surface. They gestured for her to roll backward.

She gripped the mask and regulator so they wouldn't be torn off by the entry and she held her weight-belt release so that if her buoyancy device failed and she dropped toward the bottom she could dump the weights and swim to the surface.

Okay, Rhyme, here's one for Guinness: the record for searching the most submerged crime scene.

One, two, three…

Backward into the churning water.

By the time she righted herself the others were in the water beside her and gesturing toward the buoy. In a few minutes they'd swum to it. Okay signs all around. Then a thumbs-down, which meant descend. Then they took their BCD control in their left hand and deflated the vests.

Immediately, noise became silence, motion became stillness, heavy became weightless and they drifted downward placidly along the thick rope toward the bottom.

For a moment Sachs was struck by the absolute peace of life underwater. Then the serenity was broken as she looked below her and saw the dim outline of the Fuzhou Dragon.

The image was more unsettling than she'd expected. The ship on her side, a black gash in the hull from the explosion, the rust, the peeling paint, the encrusting barnacles on the plates. Dark and jagged and foreboding – and containing the bodies of so many innocent people.

A coffin, she thought, with a clenched heart. It's a huge, metal coffin.

Sharp pain in her ears; she pinched her nose through the soft plastic portion of the mask and blew to equalize the pressure. They continued downward. As they got closer to the ship she began to hear the noises – grating and moaning as the ship's thick metal plates scraped on the rocks.

Hate that noise. Hate it, hate it. It sounded like a huge creature dying.

Her escorts were diligent. They'd stop the descent occasionally and check on her. Okay signs were exchanged and they continued downward.

At the bottom she looked up and found that the surface didn't seem as far away as she'd expected, though she recalled that water has the effect of acting like a lens and magnifying everything. A glance at her depth gauge. Ninety feet. A nine-story building. Then a glance at her pressure gauge. Jesus, she'd already used 150 pounds of air on the effortless descent.

Amelia Sachs pumped air into the BCD to neutralize her buoyancy – so that she floated level. She first pointed toward the gash in the hull and together the threesome swam toward it. Despite the pitching surface above them the currents here were gentle and they could move easily.

At the site of the explosion Sachs used her blunt knife to scrape residue from the outwardly curled metal. She placed some of the black ashy material into a plastic bag, sealed it and put that in the mesh collection bag.

She looked at the dark windows of the bridge forty feet away. Okay, Rhyme, here we go. They swam toward it.

And the pressure gauge gave her its emotionless message: 2350 pounds.

At 500 they left the bottom. No exceptions.

Because the ship was on its side the bridge door now opened upward, toward the surface. It was metal and very heavy. The two Coast Guard officers struggled to lift it and Sachs swam through the opening and down into the bridge. They lowered the door into the closed position. It clanked shut with a chilling boom and Sachs realized that she was now trapped inside the ship. Without her companions she probably couldn't open the door herself.

Forget it, she told herself, reached up to the light mounted on her wetsuit hood and clicked it on. The beam offered her faint comfort. She turned and swam away from the bridge down a dark corridor that led to the cabins.

Faint motion too from the dimness. Coming from what? Fish, eels, squid?

I don't like this, Rhyme.

But then she thought about the Ghost searching for the Changs, about the baby, Po-Yee, the Treasured Child.

Think about that, not about the darkness or confinement. Do this for her, for Po-Yee.

Amelia Sachs swam forward.

She was in hell.

No other word described it.

The black hallway was filled with sooty debris and refuse, scraps of cloth, paper, food, fish with piercing yellow eyes. And overhead, a shimmering, like ice: the thin layer of air trapped above her. The sounds were harrowing: the scraping and groaning, moans. Squeals like human voices in agony, pings and snaps. The clank of metal on metal.

A fish, gray and sleek, darted past. She gasped involuntarily at the motion and turned her head to follow it.

She found herself looking at two dull human eyes in a white lifeless face.

Sachs screamed through her regulator and jerked back. The body of a man, barefoot, his arms above his head, like a perp surrendering, floated nearby. His legs were frozen in the position of a runner's and, as the fish sped past, the small wake turned him slowly away from her.

Clank, clank.

No, she thought. I can't do this.

Already the walls were closing in on her. Plagued all her life by claustrophobia, Sachs couldn't stop thinking of what would happen if she got caught in one of these tiny passages. She'd go mad.

Two deep breaths of dry air through the regulator.

She thought of the Chang family. She thought of the toddler.

And she swam on.

The gauge: 2300 pounds of pressure.

We're doing fine. Keep going.

Clank.

That damn noise – like doors closing, sealing her shut.

Well, ignore it, she told herself. Nobody's closing any doors.

The rooms above her – on the side of the Dragon facing the surface – were not, she deduced, the Ghost's: two didn't appear to have been occupied on the voyage and one was the captain's; in this one she found seafaring memorabilia and pictures of the bald, mustachioed man she recognized as Captain Sen from the pictures tacked up on Lincoln Rhyme's wall.

Clank, clank, clank…

She swam downward to check out the rooms on the other side of the narrow corridor – facing the bottom.

As she did, her tank caught on a fire extinguisher mounted to the wall and she froze in position. Trapped in the narrow corridor she was seized with a flash of panic.

It's okay, Sachs, Lincoln Rhyme's voice said to her in that deep, lulling voice he always fell into when speaking to her through her headset at crime scenes. It's okay.

She controlled the panic and backed up, freeing herself.

The gauge told her: 2100 pounds.

Three of the cabins below her hadn't been occupied. That left only one more – it had to be the Ghost's.