Dial M for Murder

In London, wealthy Margot Mary Wendice had a brief love affair
with the American writer Mark Halliday while her husband and
professional tennis player Tony Wendice was on a tennis tour. Tony quits
playing to dedicate to his wife and finds a regular job. She decides to
give him a second chance for their marriage. When Mark arrives from
America to visit the couple, Margot tells him that she had destroyed all
his letters but one that was stolen. Subsequently she was blackmailed,
but she had never retrieved the stolen letter. Tony arrives home, claims
that he needs to work and asks Margot to go with Mark to the theater.
Meanwhile Tony calls Captain Lesgate (aka Charles Alexander Swann who
studied with him at college) and blackmails him to murder his wife, so
that he can inherit her fortune. But there is no perfect crime, and
things do not work as planned.