Lying in Wait.

Young bachelor Babee is looking after his dead mother's estate when married couple Keith and Vera move in. Babee becomes attracted to them by the beautiful Vera and the risk-taking Keith. However, at a party, Vera crashes her car, putting Keith into a coma. When Keith comes out, he is in a semi-vegetative state and must rely on Vera to look after him. Keith can't move or speak but reveals to Babee that he can still talk and starts to kill those that wronged him with Babee's help.