At once he pulled his hands out of the box, quickly peeled off the gloves, and stared at his finger. A drop of blood welled up, the sight of it so unexpected, he felt nauseated. He closed his eyes, berating himself. This was nothing—barely a prick. The mouse’s rightful vengeance for all those needles he had stuck in it. He opened his eyes again, but the nausea was still there.

I need to rest, he thought.

He recaptured the struggling mouse and thrust it into the cage. Then he removed the two bagged corpses and placed them in the refrigerator. Tomorrow, he’d deal with the problem. Tomorrow, when he felt better.

“I found this one dead today,” said Kenichi. “It is number six.”

Emma frowned at the mice in the animal habitat. They were housed in a divided cage, the males separated from the females only by a wire barrier. They shared the same air, the same food water supply. On the male side, a dead mouse floated motionless, limbs extended and rigid.

The other males were clustered at the opposite end of the enclosure, scrabbling at the screen as though frantic to escape.

“You’ve lost six mice in seventeen days?” said Emma.

“Five males. One female.” Emma studied the remaining live animals for signs of illness.

They all appeared alert, their eyes bright, with no mucus from their nostrils.

“First, let’s get this dead one out,” she said. “Then we’ll take a close look at the others.” Using the glove box, she reached into the cage and removed the corpse. It was already in rigor mortis, the legs stiff, the body inflexible. The mouth was partly open, and the tip of the tongue protruded in a soft flap of pink. It was not unusual for lab mice to die in space. On one shuttle flight in 1998, there had been a hundred percent mortality among newborn rats. Microgravity was an alien environment, and not all species adapted well.

Prior to launch, these mice would have been screened for a number of bacteria, fungi, and viruses. If this was an infection, then they had picked it up while aboard ISS. She put the dead mouse in a plastic pouch, changed gloves, and reached into the enclosure for one of the live mice. It squirmed with great vigor, showing no signs of illness. The only unusual thing was a tattered ear that had been chewed by its cage mates. She flipped over to look at its belly and gave an exclamation of surprise.

“This is a female,” she said.

“What?”

“You had a female in the male enclosure.” Kenichi leaned close to peer through the glove box window at the mouse’s genitals. The evidence was plain to see. His face flushed deep red with embarrassment.

“Last night,” he explained. “She bit me. I put her back in a hurry.”

Emma gave him a sympathetic smile. “Well, the worst that can happen is an unexpected baby boom.” Kenichi slipped on gloves and inserted his hands in the second pair of glove box armholes. “I make the mistake,” he said. “I fix it.” Together they examined the rest of the mice in the enclosure, but found no other misplaced specimens. All appeared healthy.

“This is very strange,” said Emma. “If we’re dealing with a contagious disease, there ought to be some evidence of infection.”

“Watson?” a voice called over the module intercom.

“In the lab, Griggs,” she answered.

“You’ve got priority E-mail from Payloads.”

“I’ll get it now.” She sealed off the animal enclosure and said to Kenichi, “Let me check my message. Why don’t you take out the dead mice you put in cold storage. We’ll look at them.” He nodded and floated across to the refrigerator.

At the workstation computer, she called up her priority Email.

Emma read and reread the message on the screen. Never before had she received such a strange request. Fungal contamination was not dangerous.

To incinerate the cultures seemed a drastic overreaction. She was so preoccupied by this puzzling request she paid no attention to Kenichi, who was taking the dead mice out of the refrigerator. Only when she heard him gasp did she turn to look at him.

At first all she saw was his shocked face, splattered with a foul slurry of entrails. Then she looked at the plastic bag that had burst open. In his horror, he had released it, and it floated free, hanging in the air between them.

“What is that?” she said.

He said, in disbelief, “The mouse.” But it was not a dead mouse she saw in the bag. It was a mass of disintegrated tissue, a putrefied gumbo of flesh and fur that now was leaking out foul-smelling globules.

Biohazard!

She shot the length of the module to the caution-and-warning panel and hit the button to shut off airflow between modules.

Kenichi had already opened the emergency rack and pulled out two filter masks. He tossed one to her, and she clapped it over her own mouth. They didn’t need to exchange a word, they both knew what had to be done.

Quickly they closed the hatches on either end of the module, effectively isolating the lab from the rest of the station. Then took out a biocontainment bag and carefully moved toward the drifting bag of liquefied flesh. Surface tension had bound the droplets together in one globule, if she was careful not to stir the air, she could trap it in the bag, without scattering droplets. Gently she moved containment bag over the free-floating specimen and quickly sealed it off. She heard Kenichi give a sigh of relief. Hazard contained.

“Did it leak into the refrigerator?” she asked.

“No. Only when I took it out.” He wiped his face with an alcohol swab and sealed the swab for safe disposal. “The bag, it was… you know, blown up big. Like a balloon.” The contents had been under pressure, the process of decomposition releasing gases. Through the plastic containment bag, she could see the date of death on the label. This is impossible, she thought. In just five days, the corpse had deteriorated to a puree of rotted flesh. The bag was cold to the touch, so the refrigerator was functioning. Despite cold storage, something had accelerated the body’s decomposition. Flesh-eating streptococcus? She wondered. Or another bacteria, equally destructive?

She looked at Kenichi and thought, It splashed him in the eye.

“We need to talk to your principal investigator,” she said. “The one who sent up these mice.” It was only five A.M., Pacific Daylight Time, but the voice of Dr. Michael Loomis, principal investigator for the experiment, “Conception and gestation in mice during spaceflight,” was fully and obviously concerned. He was speaking to Emma from Ames Research Center in California. Though she couldn’t see him, she could picture the man who belonged to this reedy voice, tall, energetic. A man for whom five in the morning is a normal part of his workday.

“We’ve been monitoring these animals for over a month,” said Loomis. “It’s a relatively low-stress experiment for the animals. We’d planned to mingle the males and females next week, in hopes they’d successfully mate and conceive. This research has important applications for long-term spaceflight. Planetary colonization. you can imagine, these deaths are pretty upsetting.”

“We’ve already got cultures incubating,” said Emma. “All the dead mice appear to be decomposing more quickly than they should. Based on the condition of the corpses, I’m concerned for clostridia or streptococcus infections.”