The Lonely Hearts Killer refers to Raymond Fernandez and Martha Beck, a murderous couple who lured victims through personal ads in the 1940s. Posing as lovers, they gained the trust of lonely women, then robbed and killed them, with Beck often displaying intense jealousy. They were arrested in 1949 and executed in the electric chair in 1951.

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