Hercule Poirot is bored to tears and with three weeks since his last case, is worried that his little gray cells will stop working. Captain Hastings suggest a evening at the theater to see the latest murder mystery but even that doesn't help when Poirot finds the plot to be absurd. On their return home to Whitehaven Mansions, they learn that the new occupant of the flat two floors below Poirot's has been found shot. She had only moved in that very same day and was an unknown. Poirot puts his little gray cells to good use and assists Inspector Japp of Scotland Yard in identifying the murderer.