Linimer’s fingers caressed the brass dial. Six plus four minus one choose four. The engine rang out its answer, one note in a mechanical symphony. Sixty combinators danced along the face of the machine, up and down the Hall of Computation.

Nine choose four and nine choose five is ten choose five. Six hundred fingers flew over the cogs and stops. Slanting sunbeams streamed through the high windows, making gnomons of the workers and gold dust of the whirling motes. It was evening.

The twenty-four-minute whistle blew and Linimer gave way to his four-six replacement. He was trembling. This was the night he had chosen to reveal his secret double life.

Gerson, his supervisor, was waiting at the exit. “There you are,” he said, glancing at his watch. “Ready?”

“Y-yes,” said Linimer, staring hard at the floor and trying on several expressions in turn. “I west-end the north living quarter,” he said.

“You wha-a-a-at?” Gerson bleated.

“The northwestern quarter. Where I live.”

“Oh, oh. Right, then. Lead the way.”