The Third Floor Flat

Poirot is feeling terribly bored, as he has had no murder cases at all for several weeks. He takes Hastings to see a new whodunnit at the theatre, to relieve the boredom. But just a few hours later, Poirot is disturbed in his own apartment by the strange shooting of Mrs Grant, a resident of his building, Whitehaven Mansions. Two young couples find the murdered woman's body in the third-floor flat two floors below Poirot's, and it soon appears that bigamy may be the key to the mystery. But is it?