I went quickly to the nearest public communications booth, thumbed the plate, and put through a call to Sam.

“He is not at his home number,” the master information output told me. “Should we trace him?”

“Yes, please,” I said automatically.

A moment later I slapped myself for stupidity. Of course he won’t be home, you idiot! He’s up the line in 1559!

But the master communications network had already begun tracing him. Instead of doing the sensible thing and hanging up, I stood there like a moron, waiting for the inevitable news that the master communications network couldn’t find him anywhere.

About three minutes went by. Then the bland voice said, “We have traced your party to Nairobi and he is standing by for your call. Please notify if you wish to proceed.”

“Go ahead,” I said, and Sam’s ebony features blossomed on the screen.

“Is there trouble, child?” he asked.

“What are you doing in Nairobi?” I screamed.

“A little holiday among my own people. Should I not be here?”

“Look,” I said, “I’m on my layoff between Courier jobs, and I’ve just been up the line to 1559 Istanbul, and I met you there.”

“So?”

“How can you be there if you’re in Nairobi?”

“The same way that there can be twenty-two specimens of your Arab instructor back there watching the Romans nail up Jesus,” Sam said. “Sheet, man, when will you learn to think four-dimensionally?”

“So that’s a different you up the line in 1559?”

“It better be, buster! He’s there and I’m here!” Sam laughed. “A little thing like that shouldn’t upset you, man. You’re a Courier now, remember?”

“Wait. Wait. Here’s what happened. I walked into the Covered Bazaar, see, and there you were in Moorish robes, and I let out this big whoop and ran up to you to say hello. And you didn’t know me, Sam! You started waving your scimitar, and cursing me out, and you told me in English to get the hell away from you, and—”

“Well, hey, man, you know it’s against regulations to talk to other time-travelers when you’re up the line. Unless you set out from the same now-time as the other man, you’re supposed to ignore him even if you see through his cover. Fraternization is prohibited because—”

“Yeah, sure, but it was me, Sam. I didn’t think you’d pull rules on me. You didn’t even know me, Sam!”

“That’s obvious. But why are you so upset, kid?”

“It was like you had amnesia. It scared me.”

“But I couldn’t have known you.”

“What are you talking about?”

Sam began to laugh. “The Paradox of Discontinuity! Don’t tell me they never taught you that one!”

“They said something about it, but I never paid much attention to a lot of that stuff, Sam.”

“Well, pay attention now. You know what year it was I took that Istanbul trip?”

“No.”

“It was 2056, ’55, someplace back there. And I didn’t meet you until three or four years later — this spring, it was. So the Sam you found in 1559 never saw you before. Discontinuity, see? You were working from a now-time basis of 2059, and I was working from a basis of maybe ’55, and so you were a stranger to me, but I wasn’t a stranger to you. That’s one reason why Couriers aren’t supposed to talk to friends they run into by accident up the line.”

I began to see.

“I begin to see,” I said.

“To me,” said Sam, “you were some dumb fresh kid trying to make trouble, maybe even a Time Patrol fink. I didn’t know you and I didn’t want anything to do with you. Now that I think about it a little, I remember something like that happening when I was there. Somebody from down the line bothering me in the bazaar. Funny that I never connected him with you, though!”

“I had a fake beard on, up the line.”

“That must have been it. Well, listen, are you all straightened out now?”

“The Paradox of Discontinuity, Sam. Sure.”

“You’ll remember to keep clear of old friends when you’re up the line?”

“You bet. Christ, Sam, you really terrified me with that scimitar!”

“Otherwise, how’s it going?”

“Great,” I said. “It’s really great.”

“Watch those paradoxes, kid,” Sam said, and blew me a kiss.

Much relieved, I stepped out of the booth and went up the line to 1550 to watch them build the mosque of Suleiman the Magnificent.

Themistoklis Metaxas was the chief Courier for my second time-tour of Byzantium. From the moment I met him I sensed that this man was going to play a major role in my destiny, and I was right.

Metaxas was bantam-sized, maybe 1.5 meters tall. His skull was triangular, flat on top and pointed at the chin. His hair, thick and curly, was going gray. I guess he was about fifty years old. He had small glossy dark eyes, heavy brows, and a big sharp slab of a nose. He kept his lips curled inward so that he didn’t seem to have lips at all. There was no fat on him anywhere. He was unusually strong. His voice was low and compelling.

Metaxas had charisma. Or should I call it chutzpah?

A little of both, I think. For him the whole universe revolved around Themistoklis Metaxas; suns were born only that they might shed starlight on Themistoklis Metaxas; the Benchley Effect had been invented solely to enable Themistoklis Metaxas to walk through the ages. If he ever died, the cosmos would crumble.

He had been one of the first Time Couriers ever hired, more than fifteen years ago. If he had cared to have the job, he could have been the head of the entire Courier Service by now, with a platoon of wanton secretaries and no need to battle fleas in old Byzantium. By choice, though, Metaxas remained a Courier on active duty, doing nothing but the Byzantium run. He practically regarded himself as a Byzantine citizen, and even spent his layoffs there, in a villa he had acquired in the suburbs of the early twelfth century.

He was engaged on the side in a variety of small and large illegalities; they might be interrupted if he retired as a Courier, so he didn’t retire. The Time Patrol was terrified of him and let him have his own way in everything. Of course, Metaxas had more sense than to meddle with the past in any way that might cause serious changes in now-time, but aside from that his plunderings up the line were totally uninhibited.

When I met him for the first time, he said to me, “You haven’t lived until you’ve laid one of your own ancestors.”

It was a big group: twelve tourists, Metaxas, and me. They always loaded a few extras into his tours because he was such an unusually capable Courier and in such great demand. I tagged along as an assistant, soaking up experience against my first solo trip, which would be coming next time.

Our dozen included three young and pretty single girls, Princeton co-eds making the Byzantium trip on gifts from their parents, who wanted them to learn something; two of the customary well-to-do middle-aged couples, one from Indianapolis and one from Milan; two youngish interior decorators, male and queer, from Beirut; a recently divorced response manipulator from New York, around forty-five and hungry for women; a puffy-faced little high-school teacher from Milwaukee, trying to improve his mind, and his wife; in short, the customary sampling.

At the end of the first introductory session all three of the Princeton girls, both interior decorators, and the Indianapolis wife were visibly hungering to go to bed with Metaxas. Nobody paid much attention to me.

“It will be different after the tour starts,” said Metaxas consolingly. “Several of the girls will become available to you. You do want the girls, don’t you?”

He was right. On our first night up the line he picked one of the Princeton girls for himself, and the other two resigned themselves speedily to accepting the second best. For some reason, Metaxas chose a pugnosed redhead with splashy freckles and big feet. He left for me a long, cool, sleek brunette, so flawless in every way that she was obviously the product of one of the world’s finest helix men, and a cute, cheerful honey-blonde with warm eyes, smooth flesh, and the breasts of a twelve-year-old. I picked the brunette and regretted it; she came on in bed like something made of plastic. Toward dawn I traded her for the blonde and had a better time.