Private detective Aggie St. James is particular about the clients she accepts, but when a woman is found murdered with a note that says, "St. James, find my killer," she has no choice. St. James's search for the killer leads to a dead husband, a disreputable former fiancé, and an empty mansion. Along the way she is threatened by her brother's murderous ex-wife and must help a friend who was almost killed in her apartment. Finding the murderer will require the help of a half-wild cat, a snoopy neighbor, and dogged perseverance.