When their irascible headmistress, Mrs. Plackett, and her surly brother, Mr. Godding, are poisoned at Sunday dinner, the girls of St. Etheldreda's School for Young Ladies face a dilemma. The school will almost certainly be closed and the girls sent home -- unless these seven very proper young ladies can hide the murders and convince their neighbors that nothing is wrong. But there's a murderer on the loose -- how can the girls be sure the killer won't strike again?