He looked behind him at the unadorned outer walls of the Septizodium. He stood in an alley, one of the many unmarked and unmemorable gaps between buildings in Rome. The door through which he had stumbled wasn't a real door, but a clever panel of stone. Any other time, he would never have noticed it against the mottled background of the surrounding stone, but it hung open now, and a column of black smoke spiraled up from it. There were other spires of smoke rising over the rooftop; clearly, there were other exits from the Septizodium. They might not have been plain to those who were sequestered inside, but smoke had a talent for finding a way out.