To take Poirot's mind off the fact that he has no case and his little grey cells are atrophying, Hastings takes him to the theater to see a mystery play. Poirot guesses the wrong murderer and then complains the audience wasn't given all the facts.
When they arrive home, they find out that there has been a murder two floors down, of a young woman who just moved in. The two women who lived in the same apartment line did not have their keys, and their dates go down the fire escape, but climb in the wrong window and find the body.
Strangely, the woman had left a note for one of the women in the other apartment wanting to speak with her.
Poirot works with Inspector Japp to attempt to figure out who killed this woman, and why.
Delightful mystery, with Poirot and Hastings in good form and interacting with people in the building, which one doesn't see much. Poirot also shows a lack of detachment when it comes to one of the neighbors -- he finds her lovely, and picks up that one of the men is in love with her, although she's engaged to someone else. Sweet as well as touching.
Very entertaining, and a good mystery.