"...and when I came back into the room, Mr. Valentine, it had vanished!"

Dr. Abbott's expression was as odd as the rest of him, clearly worried but still cheerful. If lab coats and absent-mindedness mean anything he was a research scientist all right. He'd lost his comb and never noticed, but that was all right because the top of his skull was mostly forehead. Evidently he needed a keeper since the government had issued one, complete with earpiece. I guess you have to make allowances for honest-to-God geniuses.

But what do I care? His cash was good.

"All right, Dr. Abbott; I'm on the job. I'll just need that retainer."

* * *

I followed his sedan to the lab uptown. His driver was a pro and made sure not to lose me, and I made it through the heavily guarded gates with a minimum of fuss, which is unusual. I've seen prisons with less security, but Dr. Abbott's word alone got me past every locked door.

Once we finally made it through the umpteen layers of security, Abbott gave me the full tour. His laboratory was a sprawling suite, complete with living quarters for himself and his three assistants. Since the incident, they'd all been confined here. There were guards, but given the security system they weren't worth considering; besides, none ever entered, the windows couldn't open, and the door was constantly monitored.

Only Abbott had been permitted to leave, and even he had been under constant surveillance all the way to my office and back. Normally he'd have been among my suspects, but he was so unworldly the concept was laughable. Besides, with his level of authority, he could've concealed the loss easily; instead he brought me in. That only left the other three, and since they couldn't get out it was a cinch the dingus was still inside the locked suite.

I interviewed each of them in turn. My goal was more to see how they'd react than try to trap anyone in a confession; they were all stressed. The portly one, Ikey, hid behind a set of straggly sidewhiskers and awful puns. Young Glenn was shy and insecure but put on such a show of abrasive rudeness you almost couldn't tell. Jenny, the only woman, peered out at the world through owl-eyed glasses and a thick curtain of hair. They were all brilliant, all introverts, and all hiding something, but that's as far as I could get.

The only topic on which anyone would open up was the project, and that got so technical they lost me. Ikey was the theory man but otherwise hopeless, Jenny's materials discoveries made the device possible, and Glenn was the practical engineer. Each detested the other two, but all three were utterly devoted to Dr. Abbott, whose genius appeared to include managing difficult personalities.

That evening I dined with Dr. Abbott and discussed the case. At my request, he'd had complete security dossiers printed, and I scanned them while asking questions. We got nowhere, and I retired early to plow through several hundred pages of light reading.

The next morning, we opened up the sealed lab to reproduce the experiment. I had them explain every step in painstaking detail, and when it got too technical they broke it down for me. Four hours into the exercise, I'd asked a thousand stupid questions and each of the three suspects now hated me more than they did each other. At least I'd accomplished that.

Over lunch with Abbott, I kept up the questions; I was determined to understand this no matter how long it took. Even his perpetual smile grew strained.

"It's really quite simple," he said. I had my doubts but stayed quiet. "You see my glasses?" he asked, handing them to me. "When you look through, the lenses distort the light, but in a way perfectly suited to my eyes. You look through and see a blur; I look and see clearly. Well, at least when they're clean," he added, taking them back and wiping them on his lab coat.

"So this dingus of yours warps the light that passes through it," I said.

"Yes, in a way that makes for perfect camouflage."

I nodded. "This may be a dumb question," I began (he winced), "but glasses have frames. Does the dingus?"

He beamed. "Actually, that's an excellent question. And yes, of course it does — not literally, but the same sort of thing. That's the beauty of our breakthrough with the X-53, because the whole point of the new design is to keep all the parts inside the warped light."

"Like putting the frames inside the lenses, or making them out of glass."

"Precisely! Again, not literally, but it would have that exact effect. Harness, control circuitry, power supply: It's entirely self-contained. Marvelous, really, and a tremendous advance over the earlier..."

He was off again, but I didn't care; I'd had an idea.

After lunch we went back to the lab, but I stopped the recreation. "If I'm wrong, we can keep going," I said, and had them kill the power. Then I opened the reaction chamber and reached inside. They tried to stop me, but I was too close.

I woke in a hospital bed; the nurses explained it had been a severe electrical shock. Later, Dr. Abbott came to see me and I found out I'd been right. The dingus had never moved; it was just invisible.

"What we hadn't realized was that the warp effect would cut off the instruments too, even though they're hard-wired and shouldn't be affected. We still have no idea why. It just sat there, self-powered, until you touched it and discharged the field. And we never suspected, because we were relying on our gauges. How ever did you figure it out?"

I smiled, then winced; my face felt sunburned. "The advantage of being dumb, Doc. You all understood all the reasons it couldn't possibly be there — and I didn't."