There might be something spooky going on right now at the baby-sitters club! The baby-sitters have been getting mysterious phone calls when they’re out on their jobs. When a phone rings and they pick up, there’s no one on the other end of the line. Claudia’s sure it’s the Phantom Caller, a jewel thief who’s been operating in the area. Claudia has always liked reading mysteries, so she and the baby-sitters decide to take action―with some very mixed results!