Jill followed. “What’s wrong?”

His laptop hung heavily from one hand, and when he landed on the sofa he let it drop to the floor beside him. He fell back against the cushions, partially reclined. He looked like he couldn’t move to either sit up or lie all the way down.

He looked seriously ill. That sparked fear and guilt in Jill about what she was doing, exposing him—exposing them both—to the altered one-minus-one. She mumbled something extraneous and went to the kitchen, wet a dish towel with cool water from the tap. His face was so white… her heart pounded violently, another overreaction. Knowing that didn’t make it go away.

When she came back, he was weakly pulling off his T-shirt, which was damp with sweat. He collapsed back on her couch, his skin clammy and slick, looking exhausted, looking green. He appeared to have come close to losing consciousness—perhaps still might. “Hot,” he panted. “Fan?”

“No, I’m sorry.”

She ran to open the windows in the living room and kitchen, hoping for a cross-breeze. And although it was a warm day, it did not seem unbearably hot to her. This thought scared her further and she ran into the bathroom and rifled for a thermometer. She took it back to the living room and knelt down by the couch. Nate’s eyes were closed.

“We should take your temperature,” she said, feeling awkward. She stuck the thermometer in his mouth and began wiping the pale skin on his face and arms with the cold cloth, the way her mother used to when she had a fever. His skin was radiating heat. He opened his eyes.

“Do you think you need to go to the hospital?”

“Just hot,” he managed around the thermometer.

“No talking. You didn’t touch your dinner. You haven’t been eating at all, Nate! You’re going to make yourself sick, and then how would we know if the experiment had anything to do with it or not?”

She spoke with annoyance to cover her fear, puttered nervously with the cloth, wiping and wiping at the long inside length of his right arm. It was so pale it glowed, skin taut against muscle. She wiped at his hand, which she held open for access, half noting its wide, creamy surface and dark rivulets of lines, the incredibly soft texture of his fingertips.

Why was time crawling all of a sudden, and how soon could she check the thermometer so she could get away? She reached up with her free hand to feel his forehead, but moving seemed to take an exorbitant amount of effort, and the distance to his forehead seemed endless. His forehead felt cold and wet. Hadn’t he just been burning up? No, it was her own hand that was damp and cold. How could she tell anything?

She should feel relieved that he appeared to be recovering, lying there looking up at her with a gaze as pressing as a stone. But a heavy, nauseous, foreboding feeling was gathering in her groin. She was the one who was sick; she was sick.

He was staring, sunk into the dark couch as though he were floating on a velvet sea. With his black curly hair and bare chest he looked like some Greek boy nymph or something, and she could not get off her knees. She suddenly thought of a million things she should go check in the house while the thermometer did its thing and the seconds crawled by. A breeze from the windows stirred the hair at her neck. She witnessed the skin on his smooth chest attenuating into a field of tiny bumps in that same breeze, and it seemed to have more clarity, more intensity of light, than anything she had ever seen. The cloth was leaden. Her hand lay heavily on his arm, immobilized.

He took the thermometer from his mouth, reached up to cup the back of her neck, pulled her down, kissed her.

At the first touch of his lips, an electric tide washed through her body. It was like being hit by a truck, the force of it; it was like being injected with hot and cold fluids at the same time. She could feel the chemicals rush madly through every part of her, from her tingling crown to the tips of her fingers and toes (suddenly numb), to her constricted chest, her trembling legs, her utter core of awareness, which was now located deep and low in her abdomen.

He surged up against her, urgent yet impossibly soft and fluid at the same time. It was as if she were melting into him, as if he were a river current sucking her down, his lips, tongue, soft and dangerous as the rushing tides. She could feel his passion, so dense the heat of it burned in her mouth like a glowing sun. Or was that her own passion? Her mouth was responding with a will of its own, seeking out every bit of him as if he were the air and she was dying with need of it. His fingertips grasped her arms, pulling her down and down even while his body arched up to meet her. It was a moment with a relentless, inescapable drive, a forward surge with only one possible end.

But. But. Her mind was strong. Her fear was stronger. She did what every human cell in her body was screaming at her not to do: she pushed him away, fell awkwardly back on her rear, scrambled to her feet, ran to her bedroom, and locked the door, choking on a sob.

She did not hear him leave, but when she finally summoned the courage to check, perhaps an hour later, he had gone.

The next day she could not, would not, avoid the lab on Nate’s account, though she’d rather have faced a firing squad. She had a speech prepared in her head and gave it, clumsily, about student–teacher relationships, about age differences, about how they both knew that certain… physical propensities… seemed to be exacerbated by the experiment and that while she didn’t blame him exactly, the important thing was to remain objective and observe the effects and not contaminate this incredibly important work with even a whiff of impropriety, and blah de blah de blah.

He didn’t look at her through most of it, held his shoulders stiff as a shield against her words. But when she was done, he turned and gave her a look of such regret and… pity that she felt herself break into a million pieces, as if her very identity were fragmenting into nothingness.

Then he began to comment on the mice and it was over.

A week later, Jill was in her office going over her mail and feeling particularly pleased by an expected and late tax rebate check. She got a cramp of genuine hunger, the first in days. She was suddenly voracious.

She crossed the campus, heading for the restaurants on University Street… and saw Nate. He was under a tree on the lawn with a girl, a student by the look of it, and they were lying side by side. He was kissing her, with great care, their bodies not touching. But the whole world existed where their lips met; anyone could see that: infinitely deep, infinitely sweet.

A gasp of pain and longing stabbed through her. She steadied herself, as if she’d been physically struck, then turned around and went back to her office, where she sat for an hour, arms wrapped around her stomach, trying to subdue the physical and emotional rampage wreacking havoc inside her body.

After that she saw less of Nate in the lab. He was always there when it was time to go over the day’s results, but at other times, when she’d normally find him just hacking around or watching the subjects, he was gone.

After a while, she was able to look back on the situation with relief. She’d avoided a nasty and highly unprofessional entanglement. She even called it courage. And when they reached the 50 percent differential in their experiment, Jill, who should have stopped there, did not. She felt reckless and a little wild. She wanted… needed… more.

She told Nate to turn it up.