Ben felt the pressure first in his ears. He held his nose, blowing out gently, and it abated. It was an odd sensation. He wasn’t moving, neither rising as he would in an airplane nor descending as he would when diving. Yet his body, convinced that it was, was reacting accordingly.

He was relieved that he wasn’t claustrophobic. Trips in the marine station’s submarine had cured him of that long ago. With only enough room (and barely even that) for two people, he’d learned to tame the fear. It had helped, of course, that he was distracted by seeing so many fascinating sea creatures, some of which he may have been the first human to witness.

There were no such distractions here. He didn’t even have a book or magazine to read; paper was forbidden in the oxygen-rich atmosphere of the chamber. A single spark could turn it into an inferno, almost certainly rendering anything inside into nothing but ash. To prevent that he would happily go without.

The pain was not yet gone. In an attempt to deal with it, he tried to break it into its component parts. He imagined the molecules of nitrogen pushing their way out of his blood like balloons, growing larger and larger as the pressure on his body grew less during his ascent with Caddie. He saw those balloons swell, filling up the soft spaces in the tissues between his joints, causing pain. They were only doing what they were designed to do, merely obeying the laws of nature. The damage they caused was unintentional, and he held them blameless.

He wished they would repay his forgiveness by voluntarily vacating his body, but they, too, were obligated to act according to the unchangeable dictates of biology and physics. And so these laws had to be thrust upon them by the men on the other side of the door, Leo and Adam, the engineers of his salvation.

He was being melodramatic. He wasn’t going to die. Probably he hadn’t even really come close. Still, there were enormous risks: paralysis, blindness, neurological devastation. He’d seen divers felled by the bends before, sometimes hours or even days after a dive. So he wasn’t taking his survival lightly; he was merely calculating his chances and finding them to be good.