Novelist Larry Donner (Billy Crystal) struggles with writer's block due to his resentment towards his ex-wife Margaret (Kate Mulgrew), who stole his book and garnered mainstream success and critical acclaim with it. Owen Lift (Danny DeVito) is a timid, middle-aged man who still lives with his overbearing, abusive mother (Anne Ramsey). Owen fantasizes of killing his mother but can't summon the courage to bring his desires into fruition. As a student in Larry's community college writing class, Owen is given advice by Larry to view an Alfred Hitchcock film to gain some insight into plot development. He sees Strangers on a Train, in which two strangers conspire to commit a murder for each other, figuring their lack of connection to the victim will, in theory, establish a perfect alibi. Having overheard Larry's public rant that he wish his ex-wife dead, Owen forms a plan to kill Margaret, believing that Larry will respond by killing his mother. He tracks Margaret down to Hawaii and follows her onto a cruise ship, apparently pushing her overboard while she tries to retrieve an earring that fell out. Owen returns from Hawaii to tell Larry of Margaret's death and that Larry now"owes" him …