TWO tired men looked at Antonia Gallo with resentment and hostility in their eyes. They wanted to go home, but she would not let them. And they knew she was right, which made it worse.

All three were in the personnel department of Oxenford Medical. Antonia, always called Toni, was facilities director, and her main responsibility was security. Oxenford was a small pharmaceuticals outfit- a boutique company, in stock market jargon-that did research on viruses that could kill. Security was deadly serious.

Toni had organized a spot check of supplies, and had found that two doses of an experimental drug were missing. That was bad enough: the drug, an antiviral agent, was top secret, its formula priceless. It might have been stolen for sale to a rival company. But another, more frightening possibility had brought the look of grim anxiety to Toni's freckled face and drawn dark circles under her green eyes. A thief might have stolen the drug for personal use. And there was only one reason for that: someone had become infected by one of the lethal viruses used in Oxenford's laboratories.

The labs were located in a vast nineteenth-century house built as a Scottish holiday home for a Victorian millionaire. It was nicknamed the Kremlin, because of the double row of fencing, the razor wire, the uniformed guards, and the state-of-the-art electronic security. But it looked more like a church, with pointed arches and a tower and rows of gargoyles along the roof.

The personnel office had been one of the grander bedrooms. It still had Gothic windows and linenfold paneling, but now there were filing cabinets instead of wardrobes, and desks with computers and phones where once there had been dressing tables crowded with crystal bottles and silver-backed brushes.

Toni and the two men were working the phones, calling everyone who had a pass to the top-security laboratory. There were four biosafety levels. At the highest, BSL4, the scientists worked in space suits, handling viruses for which there was no vaccine or antidote. Because it was the most secure location in the building, samples of the experimental drug were stored there.

Not everyone was allowed into BSL4. Biohazard training was compulsory, even for the maintenance men who went in to service air filters and repair autoclaves. Toni herself had undergone the training, so that she could enter the lab to check on security.

Only twenty-seven of the company's staff of eighty had access. However, many had already departed for the Christmas vacation, and Monday had turned into Tuesday while the three people responsible doggedly tracked them down.

Toni got through to a resort in Barbados called Le Club Beach and, after much insistence, persuaded the assistant manager to go looking for a young laboratory technician called Jenny Crawford.

As Toni waited, she glanced at her reflection in the window. She was holding up well, considering the late hour. Her chocolate-brown chalk-stripe suit still looked businesslike, her thick hair was tidy, her face did not betray fatigue. Her father had been Spanish, but she had her Scottish mother's pale skin and red-blond hair. She was tall and looked fit. Not bad, she thought, for thirty-eight years old.

"It must be the middle of the night back there!" Jenny said when at last she came to the phone.

"We've discovered a discrepancy in the BSL4 log," Toni explained.

Jenny was a little drunk. "That's happened before," she said carelessly. "But no one's ever made, like, a great big drama over it."

"That's because I wasn't working here," Toni said crisply. "When was the last time you entered BSL4?"

"Tuesday, I think. Won't the computer tell you that?"

It would, but Toni wanted to know whether Jenny's story would match the computer record. "And when was the last time you accessed the vault?" The vault was a locked refrigerator within BSL4.

Jenny's tone was becoming surly. "I really don't remember, but it will be on video." The touch-pad combination lock on the vault activated a security camera that rolled the entire time the door was open.

"Do you recall the last time you used Madoba-2?" This was the virus the scientists were working on right now.

Jenny was shocked. "Bloody hell, is that what's gone missing?"

"No, it's not. All the same-"

"I don't think I've ever handled an actual virus. I mostly work in the tissue-culture lab."

That agreed with the information Toni had. "Have you noticed any of your colleagues behaving in a way that was strange, or out of character, in the last few weeks?"

"This is like the sodding Gestapo," Jenny said.

"Be that as it may, have you-"

"No, I have not."

"Just one more question. Is your temperature normal?"

"Fuck me, are you saying I might have Madoba-2?"

"Have you got a cold or fever?"

"No!"

"Then you're all right. You left the country eleven days ago-by now you would have flu-like symptoms if anything were wrong. Thank you,]enny. It's probably just an error in the log, but we have to make sure."

"Well, you've spoiled my night." Jenny hung up.

"Shame," Toni said to the dead phone. She cradled the receiver and said, "Jenny Crawford checks out. A cow, but straight."

The laboratory director was Howard McAlpine. His bushy gray beard grew high on his cheekbones, so that the skin around his eyes looked like a pink mask. He was meticulous without being prissy, and Toni normally enjoyed working with him, but now he was bad-tempered. He leaned back in his chair and clasped his hands behind his head. "The overwhelming likelihood is that the material unaccounted for was used perfectly legitimately by someone who simply forgot to make entries in the log." His tone of voice was testy: he had said this twice before.

"I hope you're right," Toni said noncommittally. She got up and went to the window. The personnel office overlooked the extension that housed the BSL4 laboratory. The new building seemed similar to the rest of the Kremlin, with barley-sugar chimneys and a clock tower; so that it would be difficult for an outsider to guess, from a distance, where in the complex the high-security lab was located. But its arched windows were opaque, the carved oak doors could not be opened, and closed-circuit television cameras gazed one-eyed from the monstrous heads of the gargoyles. It was a concrete blockhouse in Victorian disguise. The new building was on three levels. The labs were on the ground floor. As well as research space and storage, there was an intensive-care medical isolation facility for anyone who became infected with a dangerous virus. It had never been used. On the floor above was the air-handling equipment. Below, elaborate machinery sterilized all waste coming from the building. Nothing left the place alive, except human beings.

"We've learned a lot from this exercise," Toni said in a placatory tone. She was in a delicate position, she thought anxiously. The two men were senior to her in rank and age-both were in their fifties. Although she had no right to give them orders, she had insisted they treat the discrepancy as a crisis. They both liked her, but she was stretching their goodwill to the limit. Still, she felt she had to push it. At stake were public safety, the company's reputation, and her career. "In future we must always have live phone numbers for everyone who has access to BSL4, wherever in the world they might be, so that we can reach them quickly in an emergency. And we need to audit the log more than once a year."