Firstborn (1984)

Sixteen-year-old Jake Livingston has been the man of the Livingston home since his parents divorced 2 years earlier, that is, until his mother started seeing Sam. Sam, an alcoholic and drug addict, introduces Jake’s mother to a self-destructive lifestyle. His mom, Wendy, can’t see beyond Sam’s charms or her own emotional needs, while his younger brother, Brian, succumbs to Sam’s ingratiating manner. Jake resents Sam’s constant presence in the household, however, particularly when Sam begins to establish rules and discipline for the boys and expects them to obey.

Jake becomes aware of a drug deal that Sam is engaged in, steals the drugs, and hides them. Sam verbally, then violently, begins demanding that they be returned, whereupon Wendy finally realizes that Jake was only protecting her and Brian because he didn’t want them to get hurt so she demands Sam leave. Sam starts beating up Jake, before attempting to beat Wendy, so Jake stands up to Sam and demands that he leave, threatening to kill him if he ever comes back. Sam then leaves as the family holds each other. Wendy apologizes and thanks Jake for saving the family’s lives.