From beloved author Lois Duncan comes a frightening novel about a group of students who set out to teach their malicious teacher a lesson — only to learn that one of them could be a killer. Mr. Griffin is the strictest teacher at Del Norte High, with a penchant for endless projects and humiliating students. Even straight-A student Susan can't believe how mean he is to her crush, Dave, and to the charismatic Mark Kinney. So when Dave asks Susan to help a group of students teach Mr. Griffin a lesson of their own, she goes along with them. After all, it's a harmless prank, right? But things don't go according to plan. When one "accident" leads to another and people begin to die, Susan and her friends must face the awful truth: one of them is a killer.