The Honeymoon Killers is a 1970 American crime film written and directed by Leonard Kastle, and starring Shirley Stoler and Tony Lo Bianco. Its plot follows an overweight nurse who is seduced by a handsome con man, with whom she embarks on a murder spree of single women. The film was inspired by the true story of Raymond Fernandez and Martha Beck, the notorious “lonely hearts killers” of the 1940s.

https://en.wikipedia.org/wiki/The_Honeymoon_Killers