That did seemed paranoid, even for Janus, but Marcus was curious to see the station in any case. He followed Giforte up the stairs to the second floor, then into a winding tower staircase that curved up another forty feet to a broad room at the very top. Here, the comfortable furniture and decorative touches had all been trundled out of the way, to make room for desks, chairs, and stacks of file folders. Enormous open windows—so big that glassing them in would have cost a small fortune—looked in every direction, all blocked to cracks by wooden shutters.

Five or six young men were hard at work, scribbling in books or doing calculations with small metal counters. They all had the pasty look of fellows who didn’t get out in the sun enough, and from the state of their hair and clothes, they didn’t even manage to get downstairs for a wash very often. Trays of half-eaten food were piled by the stairwell.

“This is the day shift,” Giforte explained. “Mostly coding and decoding. At night we’ve got a few lads with good eyes and quick pens to keep watch. White?”

One of the men looked up, his spectacles slightly askew. “Sir?”

“This is Colonel d’Ivoire,” Giforte said. “Colonel, this is Lieutenant White. He’s in charge of this end of the flik-flik line.”

“Flik-flik?” Marcus said.

“That’s just what the boys call it,” White said, getting to his feet. He was in his early twenties, with blue eyes and hair the color and general appearance of a haystack. Noticing Marcus’ attention, he ran one hand through it, which produced no notable improvement. “Sir. I mean, that’s what they call it, sir.”

“Why?”

White walked to one of the windows, where something a bit like a box lantern was mounted on a tripod. A lever projected from one side of the box. White pressed down on it, and something inside the box slid open with a sound like flik. When it let go, it closed. He did it again. Flik. Flik, flik.

“This is the . . . device?” Marcus said. “I thought it would be bigger.”

“It’s not actually terribly complex,” White said. “Not much more than a standard oil lamp with a mirror backing to concentrate the light. They use something similar in the theater, I understand. The shutter is finely balanced, so we can keep up a good speed, but that’s just a little bit of machinery. The real genius of the system is in the coding.”

“All this?” Marcus said, indicating the books.

“Yes, sir. The idea’s not a new one, of course. Signal fires have been used since ancient times. But Janus’ system lets us transmit a lot of information very quickly, as long as both sides are working from the same scheme.”