The Opera House in Ankh-Morpork is home to music, theatrics, and a harmless masked Ghost. But the seemingly benign spirit may be a psychopathic phantom responsible for a series of bizarre backstage deaths. Now, the operatic debut of a country girl from Lancre named Perdita X—the stage name of Agnes Nitt—is in jeopardy. The problem is, Agnes doesn’t quite look the part of an opera star. And there are two witches who want her to return home to join their coven. Granny Weatherwax and Nanny Ogg are determined to convince Agnes that life as a witch is more rewarding than the stage—especially since she’s expected to hide in the chorus and sing arias while a more petitely presentable soprano mouths the notes.

Only now they’re caught up in a murder mystery featuring masks and maniacal laughter. Yet no phantasmagoric fiend is going to run off a pair of rural hags after they've seen Ankh-Morpork. After all, the show must go on . . .