The Third Floor Flat

After a night out, Patricia Garnett, Jimmy Faulkener, Donovan Bailey, and Mildred Hope return to the home of Ms Garnett, who lives in Whitehaven Mansions. When Ms Garnett discovers she has lost her key, Bailey and Faulkener propose climbing up the coal lift, which passes through each flat, and opening Ms Garnett's front door from the inside. In doing so, however, they initially miscount the floors and end up in the flat one floor below, where they discover its occupant, Ernestine Grant, dead. Mrs Grant's body has been concealed behind the window curtain. Hercule Poirot, who also lives in the building, offers to help.

The police are called and inspect the scene. Inspector Rice informs Poirot of several findings: Mrs Grant was shot with an automatic pistol of small calibre fitted with a silencer; the pistol was found under the body but had no fingerprints on it; a silk handkerchief, imprinted with the name 'John Fraser', has been found; a note in Mrs Grant's pocket reads 'I WILL COME TO SEE YOU THIS EVENING AT HALF PAST SEVEN. J.F.'; Mrs Grant's maid went out for the evening at five o'clock and returned at about ten o'clock.

Inspector Rice believes the culprit to be John Fraser, but Poirot is unconvinced. The inspector gives Poirot permission to examine the flat. Poirot invites Bailey and Faulkener to accompany him, and they agree. Poirot uses ethyl chloride to knock Bailey briefly unconscious. He searches Bailey's pockets and finds two incriminating items: the missing flat key and a letter sent to Mrs Grant, which arrived by the late evening post. The letter is from a firm of solicitors confirming that the marriage between Bailey and Ernestine Grant some eight years before in Switzerland was lawful. Bailey, it transpires, wanted to marry Ms Garnett but his previous marriage was stopping him. By chance, his first wife moved into the same mansion block as his proposed future wife, and was threatening to tell Ms Garnett about their marriage. To stop her, Donovan killed Grant earlier in the evening but had to return for the solicitor's letter.