“It’s just a dart gun,” Charleston explained unnecessarily as he handed it over. “Certified nonlethal. Everybody’s got one.”

“It’ll do,” she assured him in a whisper. “Close the door behind me, veryquietly, and stay close to it. If you hear shots, or if I don’t knock on your door again inside five minutes, hit Redial and tell the man I just spoke with to get over here as fast as he can. Whatever happens, you stay here. Okay?”

“Okay,” he said with soldierly alacrity.

As soon as the door had closed behind her, she moved lightly up the stairs. She held the gun in her right hand, rather gingerly because the sealant between thumb and forefinger was starting to denature and it had become slightly sticky. She used her left hand to sort through her smartcards. She would still have to punch in the two combinations once her card had gone through the swipe slot, but she figured she could do that quietly enough. With luck, whoever was in her apartment wouldn’t know that he or she had company until Lisa actually opened the door.

If the light was on, she would have to keep moving while she assessed the situation, making herself as difficult a target as possible. If not, she would have to flick the switch with her left hand while keeping the gun at the ready, and then—

As soon as the door had opened by the merest crack, she knew the light was on, and she moved rapidly to her left as she pushed her way in, raising the gun to point it at the chest of the man who was rising from the armchair with an expression of startled horror on his face.

But she didn’t fire. The continuing effect of the pills had combined with her adrenaline to boost her sky-high, and she felt well and truly wired, but she still had the presence of mind to freeze her finger on the trigger.

Instead of firing the darter, she raised her left forefinger to her lips in an urgent gesture, imploring silence.

Fortunately, Chan Kwai Keung had always been quick on the uptake, and he must have been expecting her for hours. He stifled his cry of recognition and nodded eagerly, to show that he understood. Lisa used the barrel of the gun to beckon him to the door, and she closed it behind them as quietly as she could. Then she shook her head and pointed downstairs. Chan nodded again.

As soon as they reached the third-floor landing, Lisa knocked on John Charleston’s door. When he cracked it open, she thrust the gun through the narrow gap.

“It’s okay,” she said. “All sorted out. No cause for alarm.”

“Can I still keep it?” he asked tremulously—meaning, of course, the illicit gun.

“Keep what?” she replied generously.

Charleston wasn’t quite as quick on the uptake as Chan, but he was quick enough. “Oh,” he said feebly. The direction of his gaze switched to Chan’s face. “Right. Thanks. You’re okay now?”

“Fine,” she said. “Neither of us was ever here, okay?”

“Absolutely,” he assured her.

Lisa waited until she’d eased the car out on the road again before turning to Chan and saying: “What the helldo you think you’re playing at?” The adrenaline should have abated by now, but it hadn’t. The pills had thrown her entire system out of kilter, and she was locked like a crazy lemming or a snowshoe hare on the verge of a nervous breakdown. She was on the edge, and she wasn’t going to get off until she had seen the affair through to its bitter end.

Chan winced at the rawness of her tone. He seemed genuinely chastened. “I am very sorry,” he said, punctilious in his diction even now. “I did not know what to do for the best. I thought you would know, so I tried … I really had no idea those crazy people would try to snatch me the way they snatched Morgan. I was naive, I suppose—but that made me all the more anxious. As soon as I got out of the parking area, I ran like the wind. At first I expected you home in a couple of hours. Then, when you failed to turn up, I thought you must have been shot. I did not know what to do.”

“How did you get in? Those locks are supposed to be unhackable.”

“You should change your pass codes more often,” Chan chided her, “and your smartcard needs to be at least twice as smart as it is. But that is not important. Where have you been?”

“That’snot important. What’s important is why you’re playing silly cloak-and-dagger games while there’s a full-scale crisis on. What on earth have you got to hide?”

Dawn had turned to daylight now, but the light was gray and cold and utterly unwelcoming. It was less than a week to All Hallows’ Eve, but the weather should still have been relatively benign. This was like a return to the old days, before the greenhouse effect really took hold—but that was no reason for the dead not to hold to their calendar and keep to their graves. The world had no right to be turning topsy-turvy.

“They bombed Mouseworld,” Chan said in a whisper. “If it had just been Morgan, and Ed … but when I was told they had bombed Mouseworld, that was when I knew it had to be my fault. It had to be that crazy old experiment, not the ones we were doing for Ed Burdillon. If it had only been the work we were doing for Ed … but how did they ever find out?”

“I don’t have the time, Chan,” Lisa said sternly. “You’ll have to do better than this. Whatcrazy old experiment?”

“It was my idea,” he was quick to say. He continued so rapidly as the car sped along Wellsway toward Entry Hill that Lisa wondered whether her hearing had somehow gone into fast-forward. “I had to let Morgan in on it, but it was entirely my idea. We had to do it secretly, even if it meant breaking the law, because the department would never have given us permission. Mouseworld had become a sacred cow, untouchable—but that was pointless, do you see? As soon as all four populations had stabilized, there was no further point in the replication. If they had continued to behave differently, it would have been a different matter, but they did not. And there was so much more that might be done! Four cities: two experimental samples, two controls. What an opportunity! How could we let it go to waste? But the Departmental Committee could never have agreed. If there had ever been a majority to concede the principle, it would have fallen apart as soon as the question was raised as to which of countless imaginable experiments should be carried out. The only way that progress could be made was for one or two individuals to do what needed to be done in secret.All mice look alike among so many … and the people keeping track had ceased to do anything but count.It was so easy, Lisa, so very easy.”

Lisa felt completely numb. Time ceased to race and became suddenly still. So it was not unthinkable, after all, that Morgan had kept a secret from her for forty years—and not unthinkable, either, that Chan had kept it from her too. But even that revelation was marginally less shocking than the other. Morgan Miller and Chan Kwai Keung had subverted the Mouseworld experiment! They had taken it over, for their own secret purposes, without telling anyone what they were doing, or why. For thirty or forty years—presumably ever since the so-called “chaotic fluctuations” of the zero years—the four cities of Mouseworld had been running their ownexperiment instead of, or at the very least alongside of, the one they were supposed to be running. What kind of deception was that?

“Whatexperiment?” Lisa demanded tersely. She hadn’t time to digress.

Chan went on, speaking faster than he had ever spoken before, at least within earshot of Lisa. “I had developed a new and unprece-dentedly versatile system of antibody packaging. It was not veryclosely akin to the new method Edgar Burdillon has been helping to test, but it was sufficiently close to make us uncomfortable when Ed asked for our help with his new project. I am sworn to secrecy regarding that new project, of course, but I think that the broad outlines of the old experiment, at least, can be divulged without breaking that oath. I would not have you told at the time, because you were a police officer and it would have put you in an awkward ethical position, but if this is why Morgan has been kidnapped … well, it must suffice to say I thought I had devised a new and better approach to the problem of antibody packaging, and that I had high hopes for its utility. The world was still rife with natural infectious diseases in those days. I could not have been so optimistic had I come across it twenty years later, when the vast majority of those evils had been defeated by other means. I thought it an elegant method, but it involved importing a cumbersome package of new DNA into the superficial tissues of any carrier. The mouse models I constructed in order to study the efficiency of the system and its various side effects thrived, but there were certain ambiguities of effect that made me regret deeply that I could study them only in isolation, in interaction with one another. In order that the efficacy of the system could be properlytested, I needed to discover how the models would cope with a more realistic context. Do you see what I mean?”