The Norths are very pleased to see that the play in which they have invested is becoming a huge success. They are not worried when the show's star, Naomi Shaw, announces her intention to marry Mr. Bradley Fitch — even though it means she'll leave the show to follow her new husband to Europe. But someone else is worried, for the next day Fitch is found dead in his penthouse apartment, the victim of poisoning. The ensuing events draw the Norths deeper into the investigation until Pam finds herself shadowing the murder suspect down Park Avenue! Two additional murders (one a large, black cat) occur before the case is solved with the usual North finesse.