The Hot Month of August (1966)

A young man, Jason, is on his way home and meets two beautiful women, Hope and Alexis. He falls for Hope, but has sex with Alexis. He doesn't know that Alexis' husband has hired a private detective to trail her, and the man reports back to Alexis' husband about her affair with Jason. The husband kills Alexis but the police suspect Jason. He and Hope have to clear his name and find enough evidence to prove the husband is the killer.