done," I said.

"He got ten seconds out of us once last trip," Halloran said. "And he's been trying to repeat that fluke ever since. Bet you a munit to an 'F' ration that he'll be down with the section chief trying to shave off another second or two. Hey!—what's that—oh ..." He looked at me. "Disturbance in Cth yellow, straight down—shall we go?"

"Stop ship," I ordered. "Sound general quarters." There was no deceleration. We merely swapped ends as the alarm sounded, applied full power and stopped. That was the advantage of Cth—no inertia. We backtracked for three seconds and held in middle blue.

"What's going on?" Chase demanded as he came up from below. His eyes raked the instruments. "Why are we stopped?"

"Disturbance in Cth yellow, sir," I said. "We're positioned above it."

"Very good, Mr. Marsden." He took the spare helmet from the Exec's chair, clapped it on, fiddled with the controls for a moment, nodded, and took the helmet off. "Secure and resume course," he said. "That's the 'Amphitrite'—fleet supply and maintenance. One of our people."

"You sure, sir?" I asked, and then looked at the smug grin on Halloran's face and wished I hadn't asked.

"Of course," Chase said. "She's a three converter job running at full output. Since the Rebels have no three converter ships, she has to be one of ours. And since she's running at full output and only in Cth yellow, it means she's big, heavy, and awkward—which means a maintenance or an ammunition supply ship. There's an off phase beat in her number two converter that gives a twenty cycle pulse to her pattern. And the only heavy ship in the fleet with this pattern is 'Amphitrite.' You see?"

I saw—with respect. "You know all the heavies like that, sir?" I asked.

"Not all of them—but I'd like to. It's as much a part of a scoutship commander's work to know our own ships as those of the enemy."

"Could that trace be a Rebel ruse?"

"Not likely—travelling in the yellow. A ship would be cold meat this far inside our perimeter. And besides, there's no Rebel alive who can tune a converter like a Navy mechanic."

"You sure?" I persisted.

"I'm sure. But take her down if you wish."

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