When the Reverend Babbington suddenly dies after sipping one of the cocktails being served, Cartwright believes it was murder, though Strange finds no poison in his glass.

When Wills is interviewed, she recalls noticing Manders drop a newspaper cutting on nicotine and that Ellis had a birthmark on one hand; she later disappears.

As he could not divorce her under British law, he decided to conceal this knowledge by murdering Dr Strange, his oldest friend and the only one who knew about the marriage.

Cartwright used Mrs De Rushbridger as a red herring to distract from Strange's behaviour towards "Ellis", and he killed her to divert suspicion and prevent her from revealing her ignorance of the case.

Poirot reveals that the nicotine came from rose spray distilled by Cartwright at an old tower near his Cornwall residence; the equipment was found by him when Miss Milray went to destroy it.

[4] Isaac Anderson in The New York Times Book Review of 7 October 1934, said that the motive was "most unusual, if not positively unique in the annals of crime.

Since this is an Agatha Christie novel featuring Hercule Poirot as its leading character, it is quite unnecessary to say that it makes uncommonly good reading".

Mrs Christie has, quite apart from her special gift, steadily improved and matured as a writer, from the-strange-affair-of-style to this charming and sophisticated piece of prose".

Mrs Christie's Three Act Tragedy is up to her best level"; he summarised the set-up of the plot but then added, "A weak (but perhaps inevitable point) is the disappearance of a butler; the reader, that is to say, is given rather too broad a hint.

[11] The production was broadcast across five weekly episodes on BBC Radio 4 and stays predominantly faithful to the novel, with only very subtle changes being made.

Sir Charles travels to the South of France in order to get away from Egg, after initially believing she was in love with Oliver Manders, following a goodnight kiss between the two characters.

At the end of the story, once Poirot has revealed the motive and the proof of the first wife, Sir Charles storms out of the room, in order to "choose his exit".

A shaken and emotional Egg is then taken home by Manders, leaving Poirot and Satterthwaite to contemplate that they could have been the victims to the poison cocktail, at Sir Charles' party.