In the end of the 1950s, Holly Sargis is a 15-year-old teenage girl living in a small boring town called Fort Dupree in South Dakota. She lives there with her father, after her mom died of pneumonia a couple of years earlier. Her father paints signs and his relationship with Holly is quite tense ever since his wife died.
One day young Holly meets the much older Kit Carruthers, who is 25 at the time. She slowly falls for his charms and after a couple of days, she is deeply in love with him. Holly knows she can’t tell her father as Kit is 10 years her elder and he is a violent and degenerate boy.
After a while, Holly’s dad finds out about Holly and Kit's relationship, and as a punishment he shoots her dog. This spurs Kit into a rage and as he quarrels with Holly’s dad he ends up shooting and killing him. Holly and Kit then burn down the house and leave of into the badlands of Montana, hence the movie's name. They then find a small place for themselves and they live peacefully for a while until the bounty hunters catch up to them. Kit kills them and he and Holly move on to Kit’s friend Cato to take shelter. Kit also ends up killing Cato after he suspects that he might rat them out.
From then on, they are on the run. They struggle to escape law enforcement; a life Holly becomes tired of. She then decides to turn herself in, but Kit refuses. Kit ends with up in a car chase with the police, which ultimately leads to his capture and execution.
