Martha is an overweight nurse with a miserable life. Her best friend submits her name to a lonely-hearts club and Martha begins a laborious correspondence with a Spanish man, Ray, She falls madly in love with him. Ray makes no mystery what his business is: he marries lonely widows and then disappears with their money. Martha decides to move to New York with him, says goodbye to her petulant and selfish mother, and tells everybody that they are getting married. She arrives when Ray has just married a new victim. Martha, pretending to be Ray's brother, helps rob the wife. When the wife finds out she has been robbed, all she can do is pack her things and leave.
In a fit of jealousy when Ray is kissing his new wife, Martha almost drowns in a lake and ruins the scam. Martha would prefer to go back nursing, so Ray does not have to "work" but he refuses.
The next wife is asleep in the same room with Martha when she realizes that they have taken all her money. She asks to call her daughter and Martha tries to stop her. Ray, who sleeps in the living room, grabs a hammer. The wife begs him to let her make a phone call. Then she gets scared and begins to frantically dress up. Ray hands the hammer to Martha. Martha hits the poor woman twice, but she is still alive. Ray tries to strangle her, but is not strong enough to snap her neck. Martha brings a stocking and helps him tighten it around the woman's neck until her body finally gives up. In the morning, Martha cleans the floor.
The next victim is a kind woman who has a child. Martha is so jealous that she poisons her and, when she refuses to take more pills, tries to strangle her. Ray comes home just in time with the child, who sees Martha trying to kill her mom. Ray grabs a gun and shoots the woman. Then they have to eliminate the child, a dangerous witness: Martha drowns her in the wash basin. Ray, outside, hears the girl's last scream and spasms.
Martha has become a zombie. She picks up the phone and calls the police. They are arrested and will be executed.