Jacknife

Jacknife is a 1989 American film directed by David Jones and starring Robert De Niro, Ed Harris and Kathy Baker. The film focuses on a small, serious story, with emphasis on characterization and the complex tension between people in a close relationship. Stephen Metcalfe, upon whose play, Strange Snow 1982, the film was based, wrote the screenplay.

Megs finds himself attracted to Daves meek sister Martha, who lives with Dave and looks after him. This attraction leads to a love affair, much to Daves disapproval. Dave eventually vents his anger and frustration at a high school prom where Martha is a chaperone being accompanied by Megs. This leads to Dave finally facing his demons and acknowledging Megs and Martha for being there for him. Afterwards, despite initially ending what was a promising romance, Megs returns to Martha.The movie was filmed in Montreal, Canada, Meriden, Connecticut, Wallingford, Connecticut, and New Britain, Connecticut. ........

Source: Wikipedia