The Cable Street Irregulars are hired by the Unseen University to find missing roofing tiles. Amid terrible storms, they find themselves wrenched to a city familiar but strange. Who are these cultists in black robes, and where is the City Watch? Can they find their way back to the Mended Drum that they know? And can they prevent a killer from murdering everyone they know? Roleplaying and humor emphasized; knowledge of Discworld not required.