Night Watch

three,” said Sweeper.
    “Well, three’s trickier, of course, but—”
    “You’re the policeman. You guess the name of the third man, Mister Vimes.”
    Vimes hardly had to think. The answer erupted from the depths of darkest suspicion.
    “Carcer?”
    “He soon settled in, yes.”
    “The bastard was in the next cell! He even told me he’d grabbed some money.”
    “And you’re both stuck here, Mister Vimes. This isn’t your past anymore. Not exactly. It’s a past. And up there is a future. It might be your future. But it might not be. You want to go home now, leaving Carcer here and the real John Keel dead? But there’ll be no home to go to, if you could do that. Because if you do, young Sam Vimes won’t get a swift course in basic policing from a decent man. He’ll learn it from people like Sergeant Knock and Corporal Quirke and Constable Colon. And that might not be the worst of it, by a long way.”
    Vimes shut his eyes. He remembered how wet behind the ears he’d been. And Fred…well, Fred Colon hadn’t been too bad under the halfhearted timorousness and lack of imagination, but Quirke had been an evil little sod in his way, and as for Knock, well, Knock had been Fred’s teacher and the pupil wasn’t a patch on the master. What had Sam Vimes learned from Keel? To stay alert, to think for himself, to keep a place in his head free from the Quirkes and Knocks of the world, and not to hesitate about fighting dirty today if that was what it took to fight again tomorrow.
    He’s often thought he’d have been dead long ago if it wasn’t for—
    He looked up sharply at the monk.
    “Can’t tell you that, Mister Vimes,” said Lu-Tze. “Nothing’s certain, ’cos of quantum.”
    “But, look, I know my future happened, because I was there!”
    “No. What we’ve got here, friend, is quantum interference. Mean anything? No. Well…let me put it this way. There’s one past and one future. But there are two presents. One where you and your evil friend turned up, and one where you didn’t. We can keep these two presents going side by side for a few days. It takes a lot of run time, but we can do it. And then they’ll snap back together. The future that happens depends on you. We want the future where Vimes is a good copper. Not the other one.”
    “But it must’ve happened!” snapped Vimes. “I told you, I can remember it! I was there yesterday!”
    “Nice try, but that doesn’t mean anything anymore,” said the monk. “Trust me. Yes, it’s happened to you, but even though it has, it might not. ’Cos of quantum. Right now, there isn’t a Commander Vimes–shaped hole in the future to drop you into. It’s officially Uncertain. But might not be, if you do it right. You owe it to yourself, Commander. Right now, out there, Sam Vimes is learning to be a very bad copper indeed. And he learns fast.”
    The little monk stood up. “I’ll let you think about that,” he said.
    Vimes nodded, staring at the gravel garden.
    Sweeper crept away quietly and went back into the temple. He walked to the other side of the office. He removed a strange key from around his neck and inserted it into a small door. The door opened. Brilliant sunlight burst ahead of him.
    He walked on, his sandals leaving the cold flagstones and walking onto well-trodden earth in broad, hot daylight.
    The river had a different course this far back in the past, and present-day residents of Ankh-Morpork would have been surprised at how pleasant it looked seven hundred thousand years ago. Hippos sunbathed on a sandbank out in midstream and, according to Qu, were getting troublesome lately—he’d had to set up a little temporal fence around the camp at night, so that any hippos trying to wander in among the tents found themselves back in the water with a headache.
    Qu himself, his straw hat protecting his head from the hot sun, was supervising his assistants in a vined-off area. Lu-Tze sighed as he walked toward it.
    There were going to be explosions, he knew it.
    It wasn’t that he disliked Qu, the order’s Master of Devices. The man was a sort of engineering equivalent of the Abbott. The Abbott had taken thousand-year-old ideas and put them through his mind in a new way, and, as a result, the multiverse had opened for him like a flower. Qu, on the other hand, had taken the ancient technology of the Procrastinators, which could save and restore time, and had harnessed it to practical, everyday purposes, such as, yes, blowing