A thought had been fretting me for some time; I mentioned it to Mary. "A slug would not mount a cat just for the hell of it, would it?"

"I suppose not."

"But why? It doesn't make sense. But it has to make sense; everything they do makes sense, grisly sense, from their viewpoint."

"But it did make sense. They caught a human that way."

"Yes, I know. But how could they plan it? Surely there aren't enough of them that they can afford to place themselves on cats on the off chance that the cat might catch a human. Or are there enough?" I remembered the speed with which a slug on an ape's back had turned itself into two, I remembered Kansas City, saturated, and shivered.

"Why ask me, darling? I don't have an analytical brain." Which was true, in a way; there is nothing wrong with Mary's brain but she jumps logic and arrives at her answers by instinct. Me, I have to worry it out by logic.

"Drop the modest little girl act and try this on for size: the first question is, 'Where did the slug come from?' It didn't walk; it had to get to the Pirate on the back of another host. What host? I'd say it was Old John-John the Goat. I doubt if Pirate would have let any other human get close to him."

"Old John?" Mary closed her eyes, then opened them. "I can't get any feeling about it. I was never close to him."

"It does not matter; by elimination I think it must be true. Old John wore a coat when everyone else was complying with the Bare Back order . . . getting away with it because he shuns people. Ergo, he was hag-ridden before Schedule Bare Back. But that does not get me any further. Why would a slug single out a hermit way up in the mountains?"

"To capture you."

"Me?"

"To recapture you."

It made some sense. Possibly any host that ever escaped them was a marked man; in that case the dozen-odd Congressmen and any others we had rescued-including Mary-were in special danger. I'd mark that down to report for analysis. No, not Mary-the only slug that knew she had been possessed was dead.

On the other hand they might want me in particular. What was special about me? I was a secret agent. More important, the slug that had ridden me must have known what I knew about the Old Man and known that I had access to him. That would be reason enough to try to get me back. I held an emotional certainty that the Old Man was their principal antagonist; the slug must have known that I thought so; he had full use of my mind.

That slug had even met the Old Man, talked with him. Wait a minute, that slug was dead. And my theory came tumbling down.

And built up again at once. "Mary," I asked, "have you used your apartment since the morning you and I had breakfast there?"

"No. Why?"

"Don't. Don't go back there for any purpose. I recall thinking, while I was with them, that I would have to booby-trap it."

"Well, you didn't, did you? Or did you?"

"No, I did not. But it may have been booby-trapped since then. There may be the equivalent of Old John waiting, spider fashion, for you-or me-to return there." I explained to her Mcllvaine's theory about the slugs, the "group memory" idea. "I thought at the time he was spinning the dream stuff scientists are so fond of. But now I don't know; it's the only hypothesis I can think of that covers everything . . . unless we assume that the titans are so stupid that they would as soon try to catch fish in a bathtub as in a brook. Which they aren't."

"Just a moment, dear-by Dr. Mcllvaine's theory each slug is really every other slug; is that it? In other words that thing that caught me last night was just as much the one that rode you when you were with them as was the one that actually did ride you-Oh, dear, I'm getting confused. I mean-"

"That's the general idea. Apart, they are individuals; in direct conference they merge their memories and Tweedledum becomes exactly like Tweedledee. Then, if that is true, this one last night remembers everything it learned from me provided it had direct conference with the slug that rode me, or any other slug that had had, or a slug that had been linked through any number of slugs by direct conference to the slug that had ridden me, after the time it did-which you can bet it did, from what I know of their habits. It would have-the first one, I mean . . . wait a minute; this is getting involved. Take three slugs; Joe, Moe, and uh, Herbert. Herbert is the one last night; Moe is the one which-"

"Why give them names if they are not individuals?" Mary wanted to know.

"Just to keep them-No reason; let it lie that if McIlvaine is right there are hundreds of thousands, maybe millions, of slugs who know exactly who you and I are, by name and by sight and everything, know where your apartment is, where my apartment is, and where our cabin is. They've got us on a list."

"But-" She frowned. "That's a horrid thought, Sam. How would they know when to find us at the cabin? You didn't tell anybody we were going and I did not even know. Would they simply stake it out and wait? Yes, I suppose they would."

"They must have. We don't know that waiting matters to a slug; time may mean something entirely different to them."

"Like Venerians," she suggested. I nodded; a Venerian is likely as not to "marry" his own great-great-granddaughter-and be younger than his descendants. It depends on how they estivate, of course.

"In any case," I went on, "I've got to report this, including our guesses as to what is behind it, for the boys in the analytical group to play with."

I was about to go on to say that, if we were right, the Old Man would have to be especially careful, as it was he and not Mary and myself that they were after. But my phone sounded for the first time since my leave had started. I answered and the Old Man's voice cut in ahead of the talker's: "Report in person."

"We're on our way," I acknowledged. "About thirty minutes."

"Make it sooner. You use Kay Five; tell Mary to come in by Ell One. Move." He switched off before I could ask him how he had known that Mary was with me.

"Did you get it?" I asked Mary.

"Yes, I was in the circuit."

"Sounds as if the party was about to start."

It was not until we had landed that I began to realize how drastically the situation had changed. We were complying with Schedule Bare Back; we had not heard of Schedule Sun Tan. Two cops stopped us as we got out. "Stay where you are!" one of them ordered. "Don't make any sudden moves."

You would not have known they were cops, except for the manner and the drawn guns. They were dressed in gun belts, shoes, and skimpy breech clouts-little more than straps. A second glance showed their shields clipped to their belts. "Now," the same one went on, "Off with those pants, buddy."

I did not move quickly enough to suit him. He barked, "Make it snappy! There have been two shot trying to escape already today; you may be the third." "Do it, Sam," Mary said quietly. I did it. My shorts were a one-piece garment, with the underwear part built in; without them, I stood dressed in my shoes and a pair of gloves, feeling like a fool-but I had managed to keep both my phone and my gun covered up as I took off my shorts.

The cop made me turn around. His mate said, "He's clean. Now the other one." I started to put my shorts back on and the first cop stopped me.

"Hey! You looking for trouble? Leave 'em off."

I said reasonably, "You've searched me. I don't want to get picked up for indecent exposure."

He looked surprised, then guffawed and turned to his mate. "You hear that. Ski? He's afraid he'll be arrested for indecent exposure."

The second one said patiently, "Listen, yokel, you got to cooperate, see? You know the rules. You can wear a fur coat for all of me-but you won't get picked up for indecent exposure; you'll get picked up DOA. The Vigilantes are a lot quicker to shoot than we are." He turned to Mary. "Now, lady, if you please."