Most of the air trapped in the Golgotha does not, however, come bubbling up out of Lake Yamamoto. Most of it rises towards the Bubble, because that is how Goto Dengo planned it. He knows it's working because his ears begin to pop.

Eventually the water rises up into the Bubble itself, but it rises slowly, because the pressure of the air in here has become quite high already. As the water climbs, it further pressurizes the bubble of air in which Goto Dengo and the others are trapped. The pressure of the air rises steadily until it becomes equal to the pressure of the water. Then balance is achieved, and the water cannot rise any more. Another kind of balance is being reached within their bodies, as the compressed air floods into their chests, and the nitrogen in that air seeps through the membranes of their lungs and dissolves into their bloodstreams.

"Now we wait," says Goto Dengo, and shuts off his acetylene lamp, leaving them in darkness. "As long as we do not burn lamps, there is enough air in this chamber to keep us alive for several days. Captain Noda and his men will spend at least that long tidying up the Bundok site, erasing all traces of our work, and killing themselves. So we must wait, or else his men will only kill us when we appear on the shores of Lake Yamamoto. I would like to spend the time educating you on the subject of caisson disease, also known as the bends."

Two days later they set off one last, relatively small dynamite charge, blowing a hole through the wall of the Bubble that is large enough to admit a human being. On the other side, the diagonal to Lake Yamamoto begins.

Rodolfo is more terrified than anyone else, and so they send him first. Then goes Bong, and then Wing. Finally Goto Dengo leaves the foul, used-up air of the Bubble behind. Within a few moments they have found their way into the ascending diagonal tunnel. They begin to swim uphill through total darkness. All of them are trailing their hands against the tunnel ceiling, feeling for the opening of the first vertical shaft. Rodolfo is supposed to stop when he feels it, but the others must also be alert in case Rodolfo misses.

They thud into one another in the darkness like a loosely connected train bumping to a halt. Rodolfo has stopped-with any luck, he has found the first vertical shaft. Wing finally moves forward, and Goto Dengo follows straight up the vertical shaft and finally into a bulb at its top where a bubble of air has been trapped. The bulb is just barely wide enough to accommodate four men. They pause there, all jammed together in a cluster of bodies, heaving as they exhale the nitrogen— and carbon-dioxide-tainted air that they've been living on for the last sixty seconds, and breathe in fresh lungfuls. Goto Dengo feels his ears popping as pressure is relieved.

They have covered only a small fraction of the four hundred and fifty meters that separate Golgotha from the lake horizontally.But half of the hundred-meter verticaldistance has already been covered. That is, the pressure of the air they are breathing in this chamber is only half of what it was in the Bubble.

Goto Dengo is not a diver, and knows very little of diving medicine. But his father used to speak of how caissons were used to send workers deep underwater, to build things or to mine. That is how he learned about caisson disease, and how he learned the rule of thumb that most men will not suffer its symptoms if you have them decompress for a while at half the original air pressure. If they stop and breathe for a while, the nitrogen will come out of the tissues. Once this is done, the air pressure may be halved again.

In the Bubble, the air pressure was nine or ten atmospheres. Here in the first chamber, it's more like five. But there's not much air in this one-just enough to let them breathe for fifteen or twenty minutes, and bleed nitrogen out of their tissues, and get lungfuls of air for the next leg of the swim.

"Okay," Goto Dengo says, "we go." He finds Rodolfo in the darkness and slaps him encouragingly on the shoulder. Rodolfo takes a series of deep breaths, getting ready, and Goto Dengo recites the numbers that they all know by heart: "Twenty-five strokes straight. Then the tunnel bends up. Forty strokes up a steep hill. Where the tunnel bends again, you go straight up to the next air chamber."

Rodolfo nods, crosses himself, and then does a somersault in the water and kicks himself downwards. Then goes Bong, then Wing, and finally Goto Dengo.

This leg is very long. The last fifteen meters is a vertical ascent into the air chamber. Goto Dengo had hoped that the natural buoyancy of their bodies would make this easy, even if they were on the verge of drowning. But as he is kicking up the narrow shaft, pushing frantically on the feet of Wing, who is above him and not going as fast as he would like, he feels a growing panic in his lungs. Finally he understands that he must fight the urge to hold his breath-that his lungs are filled with air at a much higher pressure than the water around him, and that if he doesn't let some of that air out, his chest will explode. So against his instinct to save that precious air, he lets it boil out of his mouth. He hopes that the bubbles will pass by the faces of the men above him and give them the idea too. But shortly after he does it, they all stop moving entirely.

For perhaps ten seconds Goto Dengo is trapped in total darkness in a water-filled vertical hole in the rock that is not much wider than his own body. Of all the things he has experienced in the war, this is the worst. But just as he gives up and prepares to die, they begin moving again. They are half dead when they get to the breathing chamber.

If Goto Dengo's calculations were right, then the pressure in here should be no more than two or three atmospheres. But he is beginning to doubt those calculations. When he has breathed in enough air to restore full consciousness, he's aware of sharp pains in his knees, and it's clear from the sounds that the others are making that they are suffering the same way.

"This time we wait as long as we can," he says.

The next leg is shorter, but it's made more difficult by the pain in their knees. Again Rodolfo goes first. But when Goto Dengo rises up into the next air chamber, about one and a half atmospheres above normal, only Bong and Wing are there.

"Rodolfo missed the opening," Bong says. "I think he went too far-up the ventilation shaft!"

Goto Dengo nods. Only a few meters beyond where they turned into this passage is a ventilation shaft that goes all the way to the surface. It has a sharp sideways jog in the middle that Goto put there so that when Captain Noda filled it up with rubble (which he has presumably done by now), the diagonal tunnel-their escape route-would not be blocked. If Rodolfo went up that shaft, he found a cul-de-sac, with no air bubble in the top.

Goto Dengo doesn't have to tell the others that Rodolfo is dead. Bong crosses himself and says a prayer. Then they stay for a while and take advantage of the air that Rodolfo should be sharing. The pain in Goto Dengo's knees becomes sharper, but after a while it plateaus.

"From here, only small changes in altitude, not much need to decompress. Mostly we swim for distance now," he says. They still have more than three hundred horizontal meters to cover, pierced with four more shafts for air. The last of these doubles as a legitimate ventilation shaft.

So from there on it is just swimming and resting, swimming and resting, until finally the walls of the tunnel peel away from them and they find themselves in Lake Yamamoto.

Goto Dengo breaks the surface and does nothing for a long time but tread water and breathe clean air. It is nighttime, and for the first time in a year, Bundok is quiet, except for the sound of Bong, kneeling on the shore of the lake, making the sign of the cross and mumbling prayers as fast as his lips can move.

Wing has already departed, without so much as a good-bye. This is shocking to Goto Dengo until he realizes what it means: he, too, is free to go. As far as the world knows, he is dead, all of his obligations discharged. For the first time in his life, he can do whatever he wants.

He swims to the shore, gets up on his feet, and starts walking. His knees hurt. He cannot believe that he has come through all of this, and his only problem is sore knees.