Pop shrugged. "They wouldn't find much. I had postponed my final paper after the-humiliating-reception my preliminary paper received. I worked on it only at home, or here, and moved notes made in Logan to our basement here each time we came down."

"Any missing here?"

"I am certain this place has not been entered. Not that papers would matter; I have it in my head. The continua apparatus has not been touched."

"Zebadiah, is Doctor Brain a 'Black Hat'?" I asked.

"I don't know, Deety. He may be a stooge in their hire. But he's part of their

plot, or they would not have risked forging a letter to put him into Hilda's house. Jake, how difficult is it to steal your professional stationery?"

"Not difficult. I don't keep a secretary; I send for a stenographer when I need one. I seldom lock my office when I'm on campus."

"Deety, can you scrounge pen and paper? I want to see how Jake signs 'Jake."

"Sure." I fetched them. "Pop's signature is easy; I often sign it. I hold his power of attorney."

"It's the simple signatures that are hardest to forge well enough to fool a handwriting expert. But their scheme did not require fooling an expert-phrasing the note was more difficult....ince Hilda accepted it as ringing true."

"It does ring true, Son; it is very like what I would have said had I written such a note to Hilda."

"The forger probably has read many of your letters and listened to many of your conversations. Jake, will you write 'Jake' four or five times, the way you sign a note to a friend?"

Pop did so, my husband studied the specimens. "Normal variations." Zebadiah then signed "Jake" about a dozen times, looked at his work, took a fresh sheet, signed "Jake" once, passed it to Aunt Hilda. "Well, Sharpie?"

Aunt Hilda studied it. "It wouldn't occur to me to question it-on Jacob's stationary under a note that sounded like his phrasing. Where do we stand now?"

"Stuck in the mud. But we have added data. At least three are involved, two 'Black Hats' and Doctor Brain, who may or may not be a 'Black Hat.' He is, at minimum, a hired hand, an unwitting stooge, or a puppet they can move around like a chessman.

"While two plus 'Brainy' is minimum, it is not the most probable number. This scheme was not whipped up overnight. It involves arson, forgery, boobytrapping a car, wiretapping, theft, and secret communications between points widely separated, with coordinated criminal actions at each end-and it may involve doing in my cousin Zebulon. We can assume that the 'Black Hats' know that I am not the Zeb Carter who is the n-dimensional geometer; I'm written off as a bystander .who got himself killed.

"Which doesn't bother them. These playful darlings would swat a fly with a sledgehammer, or cure a cough with a guillotine. They are smart, organized, efficient, and vicious-and the only clue is an interest in six-dimensional nonEuclidean geometry.

"We don't have a glimmer as to 'who'-other than Doctor Brain, whose role is unclear. But, Jake, I think I know 'why'-and that will lead us to 'who."

"Why, Zebadiah?" I demanded.

"Princess, your father could have worked on endless other branches of mathematics and they would not have bothered him. But he happened-I don't mean chance; I don't believe in 'chance' in this sense-he worked on the one variety of the endless possible number of geometries-the only one that correctly describes how space-time is put together. Having found it, because he is a genius in both theory and practice, he saw that it was a means by which to build a simple craft-amazingly simple, the greatest invention since the wheel-a space-time craft that offers access to all universes to the full Number of the Beast. Plus undenumerable variations of each of those many universes.

"We have one advantage."

"I don't see any advantage! They're shooting at my Jacob!"

"One strong advantage, Sharpie. The 'Black Hats' know that Jake has worked out this mathematics. They don't know that he has built his spacetime tail-twister; they think he has just put symbols on paper. They tried to discredit his work and were successful. They tried to kill him and barely missed. They probably think Jake is dead-and it seems likely that they have killed Ed. But they don't know about Snug Harbor."

"Why do you say that, Zeb? Oh, I hope they do not!-but why do you feel sure?"

"Because these blokes aren't fooling. They blew up your car and burned your flat; what would they do here?-if they knew. An A-bomb?"

"Son, do you think that criminals can lay hands on atomic weapons?"

"Jake, these aren't criminals. A 'criminal' is a member of the subset of the larger set 'human beings.' These creatures are not human."

"Eh? Zeb, your reasoning escapes me."

"Deety. Run it through the computer. The one between your ears."

I did not answer; I just sat and thought. After several minutes of unpleasant thoughts I said, "Zebadiah, the 'Black Hats' don't know about the apparatus in our basement."

"Conclusive assumption," my husband agreed, "because we are still alive."

"They are determined to destroy a new work in mathematics... and to kill the brain that produced it."

"A probability approaching unity," Zebadiah again agreed.

"Because it can be used to travel among the universes."

"Conclusive corollary," my husband noted.

"For this purpose, human beings fall into three groups. Those not interested in mathematics more complex than that needed to handle money, those who know a bit about other mathematics, and a quite small third group who could understand the possibilities."

"Yes."

"But our race does not know anything of other universes so far as I know."

"They don't. Necessary assumption."

"But that third group would not try to stop an attempt to travel among the universes. They would wait with intellectual interest to see how it turned out. They might believe or disbelieve or suspend judgment. But they would not oppose; they would be delighted if my father succeeded. The joy of intellectual discovery-the mark of a true scientist."

I sighed and added, "I see no other grouping. Save for a few sick people, psychotic, these three subsets complete the set. Our opponents are not psychotic; they are intelligent, crafty, and organized."

"As we all know too well," Zebadiah echoed.

"Therefore our opponents are not human beings. They are alien intelligences

from elsewhere." I sighed again and shut up. Being an oracle is a no-good profession!

"Or elsewhen. Sharpie, can you kill?"

"Kill whom, Zebbie? Or what?"

"Can you kill to protect Jake?"

"You bet your frimpin' life I'll kill to protect Jacob!"

"I won't ask you, Princess; I know Dejah Thoris." Zebadiah went on, "That's the situation, ladies. We have the most valuable man on this planet to protect. We don't know from what. Jake, your bodyguard musters two Amazons, one small, one medium large, both probably knocked up, and one Cowardly Lion. I'd hire the Dorsai if I knew their P.O. Box. Or the Gray Lensman and all his pals. But we are all there are and we'll try! Avete, alieni, nos morituri vos spernimus! Let's break out that champagne."

"My Captain, do you think we should?" I asked. "I'm frightened."

"We should. I'm no good for more work today, and neither is Jake. Tomorrow we'll start installing the gadget in Gay Deceiver, do rewiring and reprogramming so that she will work for any of us. Meanwhile we need a couple of laughs and a night's sleep. What better time to drink life to the dregs than when we know that any hour may be our last?"

Aunt Hilda punched Zebadiah in the ribs. "Yer dern tootin', Buster! I'm going to get giggle happy and make a fool of myself and then take my man and put him to sleep with Old Mother Sharpie's Time-Tested Nostrum. Deety, I prescribe the same for you."