She felt a rush of panic, a sudden feeling of being a long way up with nothing supporting her; the bottom was far, far below. She was treading water, her head and shoulders sticking up through the open trapdoor into the air, waiting for her panic to subside. When it did, she took three deep breaths, closed her mouth tight, and dived beneath the surface.

Louise could see clearly, and her eyes didn’t sting at all. She looked around, trying to spot the man, but there were so many pieces of acrylic, and—

There he was.

He had indeed floated up, and there was a small gap—maybe fifteen centimeters—between the top of the water and the deck above. Normally it was filled with ultrapure nitrogen. The poor guy must be dead; three breaths of that would be fatal. A sad irony: he probably fought his way to the surface, thinking he could find air, only to be killed by the gas he inhaled there. Breathable air from the open trapdoor must now be mixing with the nitrogen, but presumably it was too late to help him.

Louise pushed her own head and shoulders up through the trapdoor again. She could see Paul, desperately waiting for her to say something—anything. But there was no time for that. She gulped more air, filling her lungs as much as she could, then dived under. There wasn’t enough room for her to keep her nose above water without constantly banging her head into the metal roof as she swam. The man was about ten meters away. Louise kicked her feet, covering the distance as quickly as she could, and—

A cloud in the water. Something dark.

Mon dieu!

It was blood.

The cloud surrounded the man’s head, obscuring his features. He wasn’t moving at all; if he were still alive, he was surely unconscious.

Louise craned to get her mouth and nose into the air gap. She took one tentative breath—but there was plenty of breathable air there now—then grabbed the man’s arm. Louise rolled the fellow over—he’d been floating facedown—so that his nose was sticking up into the air gap, but it seemed to make no difference. There was no spluttering from him, no sign that he was still breathing.

Louise dragged him through the water. It was tough work: the man was quite stocky, and he was fully dressed; his clothes were waterlogged. Louise didn’t have time to notice much, but it did register on her that the man wasn’t wearing coveralls or safety boots. He couldn’t possibly be one of the nickel miners, and although Louise had only gotten a fleeting glimpse of the man’s face—a white guy, blond beard—he wasn’t from SNO, either.

Paul must have been crouching on the deck above. Louise could see his head sticking into the water; he was watching as Louise and the man came closer. Under other circumstances, Louise would have gotten the injured person out of the water before she herself left it, but the trapdoor was only big enough for one of them to go through at a time, and it would take both her and Paul to drag this large man out.

Louise let go of the man’s arm and stuck her head up through the trapdoor, Paul having now backed off from it. She took a moment just to breathe; she was exhausted from pulling the man through the water. And then she put her palms flat on the wet deck and began to lift herself up and out. Paul crouched down again and helped Louise onto the deck, then they turned back to the man.

He had started to drift away, but Louise managed to grab his arm and drag him back under the opening. Louise and Paul then struggled to get him out, finally succeeding in lifting him onto the deck. He was still bleeding; the injury was clearly to the side of his head.

Paul immediately knelt next to the man and began administering mouth-to-mouth resuscitation, his cheek getting slick with blood each time he turned to see if the man’s broad chest was rising.

Louise, meanwhile, found the man’s right wrist and searched for a pulse. There didn’t—no, no, wait! There was! There was a pulse.

Paul continued to blow air into the man’s mouth, over and over again, and finally the man began to gasp on his own. Water and vomit came pouring out of him. Paul turned his head sideways, and the liquid he was ejecting mixed with the blood on the deck, washing some of it away.

The man still seemed to be unconscious, though. Louise, soaking wet, almost naked, and still chilled from the water, was starting to feel quite self-conscious. She struggled back into her jumpsuit and zipped it up—Paul watching her, she knew, even while he pretended not to.

It would still be a while before Dr. Montego arrived. SNO wasn’t just two kilometers down; it was also a kilometer and a quarter horizontally from the nearest elevator, at mineshaft number nine. Even if the lift cage had been at the top—and there was no guarantee it would have been—it would still take Montego twenty-odd minutes to get here.

Louise thought she should get the man out of his wet clothes. She reached for the front of his charcoal gray shirt, but—

But there were no buttons—and no zipper. It didn’t appear to be a pullover, even though it was collarless, and—

Ah, there they were! Hidden snaps running along the tops of the broad shoulders. Louise tried to undo them, but they didn’t budge. She glanced down at the man’s pants. They seemed to be dark olive green, although they might have been much lighter if dry. But there was no belt; instead, a series of snaps and folds encircled the waist.

It suddenly occurred to Louise that the man might be suffering from the bends. The detector chamber was thirty meters deep; who knew how far down he’d gone or how quickly he’d come up? Air pressure this much below Earth’s surface was 130 percent of normal. At that moment, Louise couldn’t figure out how that would affect whether someone got the bends, but it did mean the man would now be receiving a higher concentration of oxygen than he would have up top, and that surely must be to the good.

There was nothing to do now but wait; the man was breathing, and his pulse had strengthened. Louise finally had a chance to really look at the stranger’s face. It was broad but not flat; rather, the cheekbones trailed back at an angle. And his nose was gargantuan, almost the size of a clenched fist. The man’s lower jaw was covered by a thick, dark blond beard, and straight blond hair was plastered across his forehead. His facial features were vaguely Eastern European, but with Scandinavian rather than olive coloring. The wide-spaced eyes were closed.

“Where could he possibly have come from?” asked Paul, now sitting cross-legged on the deck next to the man. “No one should have been able to get down here, and—”

Louise nodded. “And even if he could, how would he get inside the sealed detector chamber?” She paused and brushed hair out of her eyes—realizing for the first time that she’d lost her hair net while swimming in the tank. “You know, the heavy water is ruined. If he survives this stunt, he’ll face one heck of a lawsuit.”

Louise found herself shaking her head. Who could this man be, anyway? Maybe a Native Canadian zealot—an Indian who felt the mining was interfering with sacred ground. But the man’s hair was blond, rare among Natives. Nor was this a youthful prank gone bad; the guy looked to be about thirty-five.

It was possible he was a terrorist or an antinuclear protester. But although Atomic Energy of Canada Limited had indeed supplied the heavy water, there was no nuclear work done at this site.

Whoever he was, Louise reflected, if he did finally die from his injuries, he’d be a prime candidate for the Darwin Awards. This was classic evolution-in-action stuff: a person who did something so incredibly stupid it cost him his own life.