Finding a cause worth dying for is no great trick—the Universe is full of them. Finding one worth living for is the genuine problem! In the region of the Coal Sack Nebula, on the dead fourth planet of a star called Tyban, Captain Steffens of the Mapping Command stood counting buildings. Eleven. No, twelve. He wondered if there was any significance in the number. He had no idea. "What do you make of it?" he asked. Lieutenant Ball, the executive officer of the ship, almost tried to scratch his hea