In 1964, Richard Kuklinski dates Deborah Pellicotti and kills a man that made an offensive comment about her during a game of pool. The violent Kuklinski works dubbing porn films but he tells to Deborah that he dubs Disney cartoons. Soon they get married and have two daughters. When his boss Roy Demeo closes the laboratory where Kuklinski works, he is invited to work as contract hit man after a test killing a homeless man. Along the years he works for Roy but he falls in disgrace when he lets a teenager hooker that witnessed a killing freely go, since he does not kill children. Kuklinski begins to work independently as a free-lancer irritating Roy who threatens his family and him. In 1986, Kuklinski is arrested by the police after committing more than one hundred murders.