The Alphabet Murders

The Alphabet Murders is a British detective film based on the novel The A.B.C. Murders by Agatha Christie, starring Tony Randall as Hercule Poirot.

As he and Captain Hastings look into the crimes, a beautiful woman with an interesting monogram named Amanda Beatrice Cross becomes the focus of their investigation, at least until she leaps into the Thames.The part of Poirot had originally been intended for Zero Mostel but the film was delayed because Agatha Christie objected to the script. The film varies significantly from the novel and emphasises comedy, the specialty of director Frank Tashlin. Poirot is given buffoonish characteristics, while still remaining a brilliant detective. ........

Source: Wikipedia