ARM by Larry Niven Page B

step off with it, and float down. But that wouldn't work. Not if it falls five hundred times as fast. He'd have been killed.”
    “Losing the machine maybe saved his life.”
    “But how did he get out ?”
    Bera laughed at my frustration. “Couldn't his niece be the one?”
    “Sure, she could have killed her uncle for the money. But I can't see how she'd have a motive to wipe the computer. Unless—”
    “Something?”
    “Maybe. Never mind.” Did Bera ever miss this kind of manhunting? But I wasn't ready to discuss this yet; I didn't know enough. “Tell me more about the machine. Can you vary that five-hundred-to-one ratio?”
    He shrugged. “We tried adding more batteries. We thought it might boost the field strength. We were wrong; it just expanded the boundary a little. And using one less battery turns it off completely. So the ratio seems to be constant, and there do seem to be quantum levels involved. We'll know better when we build another machine.”
    “How so?”
    “Well, there are all kinds of good questions,” Bera said. “What happens when the fields of two generators intersect? They might just add, but maybe not. That quantum effect ... And what happens if the generators are right next to each other, operating in each other's accelerated time? The speed of light could drop to a few feet per second. Throw a punch and your hand gets shorter!”
    “That'd be kicky, all right.”
    “Dangerous, too. Man, we'd better try that one on the moon!”
    “I don't see that.”
    “Look, with one machine going, infrared light comes out violet. If two machines were boosting each other's performance, what kind of radiation would they put out? Anything from X rays to antimatter particles.”
    “An expensive way to build a bomb.”
    “Well, but it's a bomb you can use over and over again.”
    I laughed. “We did find you an expert,” I said. “You may not need Sinclair's tapes. Bernath Peterfi says he was working with Sinclair. He could be lying—more likely he was working for him, under contract—but at least he knows what the machine does.”
    Bera seemed relieved at that. He took down Peterfi's address. I left him there in the laboratory, playing with his new toy.
* * * *
    The file from the city morgue was sitting on my desk, open, waiting for me since this morning. Two dead ones looked up at me through sockets of blackened bone, but not accusingly. They had patience. They could wait.
    The computer had processed my search pattern. I braced myself with a cup of coffee, then started leafing through the thick stack of printout. When I knew what had burned away two human faces, I'd be close to knowing who. Find the tool, find the killer. And the tool must be unique or close to it.
    Lasers, lasers—more than half the machine's suggestions seemed to be lasers. Incredible the way lasers seemed to breed and mutate throughout human industry. Laser radar. The laser guidance system on a tunneling machine. Some suggestions were obviously unworkable, and one was a lot too workable.
    A standard hunting laser fires in pulses. But it can be jiggered for a much longer pulse or even a continuous burst.
    Set a hunting laser for a long pulse and put a grid over the lens. The mesh has to be optically fine, on the order of angstroms. Now the beam will spread as it leaves the grid. A second of pulse will vaporize the grid, leaving no evidence. The grid would be no bigger than a contact lens; if you didn't trust your aim, you could carry a pocketful of them.
    The grid-equipped laser would be less efficient, as a rifle with a silencer is less efficient. But the grid would make the murder weapon impossible to identify.
    I thought about it and got cold chills. Assassination is already a recognized branch of politics. If this got out— But that was the trouble; someone seemed to have thought of it already. If not, someone would. Someone always did.
    I wrote up a memo for Lucas Garner. I couldn't think of anyone better qualified to