Tolland stood knee-deep in water on the engine box of the sinking Triton and searched his brain for some way to save Rachel.

Don't let the sub sink!

He looked back toward the Goya, wondering if there were any way to get a winch connected to the Triton to keep it near the surface. Impossible. It was fifty yards away now, and Pickering was standing high on the bridge like a Roman emperor with a prime seat at some bloody Colosseum spectacle.

Think! Tolland told himself. Why is the sub sinking?

The mechanics of sub buoyancy were painfully simple: ballast tanks pumped full of either air or water adjusted the sub's buoyancy to move it up or down in the water.

Obviously, the ballast tanks were filling up.

But they shouldn't be!

Every sub's ballast tanks were equipped with holes both topside and underneath. The lower openings, called "flooding holes," always remained open, while the holes on top, "vent valves," could be opened and closed to let air escape so water would flood in.

Maybe the Triton's vent valves were open for some reason? Tolland could not imagine why. He floundered across the submerged engine platform, his hands groping one of the Triton's ballast trim tanks. The vent valves were closed. But as he felt the valves, his fingers found something else.

Bullet holes.

Shit! The Triton had been riddled with bullets when Rachel jumped in. Tolland immediately dove down and swam beneath the sub, running his hand carefully across the Triton's more important ballast tank-the negative tank. The Brits called this tank "the down express." The Germans called it "putting on lead shoes." Either way, the meaning was clear. The negative tank, when filled, took the sub down.

As Tolland's hand felt the sides of the tank, he encountered dozens of bullet holes. He could feel the water rushing in. The Triton was preparing to dive, whether Tolland liked it or not.

The sub was now three feet beneath the surface. Moving to the bow, Tolland pressed his face against the glass and peered through the dome. Rachel was banging on the glass and shouting. The fear in her voice made him feel powerless. For an instant he was back in a cold hospital, watching the woman he loved die and knowing there was nothing he could do. Hovering underwater in front of the sinking sub, Tolland told himself he could not endure this again. You're a survivor, Celia had told him, but Tolland did not want to survive alone… not again.

Tolland's lungs ached for air and yet he stayed right there with her. Every time Rachel pounded on the glass, Tolland heard air bubbles gurgling up and the sub sank deeper. Rachel was yelling something about water coming in around the window.

The viewing window was leaking.

A bullet hole in the window? It seemed doubtful. His lungs ready to burst, Tolland prepared to surface. As he palmed upward across the huge acrylic window, his fingers hit a piece of loose rubber caulking. A peripheral seal had apparently been jarred in the fall. This was the reason the cockpit was leaking. More bad news.

Clambering to the surface, Tolland sucked in three deep breaths, trying to clear his thoughts. Water flowing into the cockpit would only accelerate the Triton's descent. The sub was already five feet underwater, and Tolland could barely touch it with his feet. He could feel Rachel pounding desperately on the hull.

Tolland could think of only one thing to do. If he dove down to the Triton's engine box and located the high-pressure air cylinder, he could use it to blow the negative ballast tank. Although blowing the damaged tank would be an exercise in futility, it might keep the Triton near the surface for another minute or so before the perforated tanks flooded again.

Then what?

With no other immediate option, Tolland prepared to dive. Pulling in an exceptionally deep breath, he expanded his lungs well beyond their natural state, almost to the point of pain. More lung capacity. More oxygen. Longer dive. But as he felt his lungs expand, pressuring his rib cage, a strange thought hit him.

What if he increased the pressure inside the sub? The viewing dome had a damaged seal. Maybe if Tolland could increase the pressure inside the cockpit, he could blow the entire viewing dome off the sub and get Rachel out.

He exhaled his breath, treading water on the surface a moment, trying to picture the feasibility. It was perfectly logical, wasn't it? After all, a submarine was built to be strong in only one direction. They had to withstand enormous pressure from the outside, but almost none from within.

Moreover, the Triton used uniform regulator valves to decrease the number of spare parts the Goya had to carry. Tolland could simply unsnap the high pressure cylinder's charging hose and reroute it into an emergency ventilation supply regulator on the port side of the sub! Pressurizing the cabin would cause Rachel substantial physical pain, but it might just give her a way out.

Tolland inhaled and dove.

The sub was a good eight feet down now, and the currents and darkness made orienting himself difficult. Once he found the pressurized tank, Tolland quickly rerouted the hose and prepared to pump air into the cockpit. As he gripped the stopcock, the reflective yellow paint on the side of the tank reminded him just how dangerous this maneuver was:

Three thousand pounds per square inch, Tolland thought. The hope was that the Triton's viewing dome would pop off the sub before the pressure in the cabin crushed Rachel's lungs. Tolland was essentially sticking a high-powered fire hose into a water balloon and praying the balloon would break in a hurry.

He grabbed the stopcock and made up his mind. Suspended there on the back of the sinking Triton, Tolland turned the stopcock, opening the valve. The hose went rigid immediately, and Tolland could hear the air flooding the cockpit with enormous force.

Inside the Triton, Rachel felt a sudden searing pain slice into her head. She opened her mouth to scream, but the air forced itself into her lungs with such painful pressure that she thought her chest would explode. Her eyes felt like they were being rammed backward into her skull. A deafening rumble tore through her eardrums, pushing her toward unconsciousness. Instinctively, she clenched her eyes tight and pressed her hands over her ears. The pain was increasing now.

Rachel heard a pounding directly in front of her. She forced her eyes open just long enough to see the watery silhouette of Michael Tolland in the darkness. His face was against the glass. He was motioning for her to do something.

But what?

She could barely see him in the darkness. Her vision was blurred, her eyeballs distorted from the pressure. Even so, she could tell the sub had sunk beyond the last flickering fingers of the Goya's underwater lights. Around her was only an endless inky abyss.

Tolland spread himself against the window of the Triton and kept banging. His chest burned for air, and he knew he would have to return to the surface in a matter of seconds.

Push on the glass! he willed her. He could hear pressurized air escaping around the glass, bubbling up. Somewhere, the seal was loose. Tolland's hands groped for an edge, something to get his fingers under. Nothing.

As his oxygen ran out, tunnel vision closed in, and he banged on the glass one last time. He could not even see her anymore. It was too dark. With the last of the air in his lungs, he yelled out underwater.

"Rachel… push… on… the… glass!"

His words came out as a bubbling, muted garble.