In the 1970s Midwest, teenaged Bobbie, a methamphetamine addict, attempts to rob several vending machines at a local college, but is confronted by a night guard who brutally attacks him. The fight ends with Bobbie stabbing the guard to death. A severely injured Bobbie returns to the flophouse of his older girlfriend, Rosie, who contacts Mel, a streetwise middle-aged thief and part-time drug dealer, for help. [Mel] gives Bobbie heroin to ease his pain.
After Bobbie heals, Mel and his heroin-addicted girlfriend Sid take Bobbie and Rosie under their wing. The two commit several drug heists, including one at a small clinic which accrues them a significant amount of money. While on the run, Rosie discovers she is pregnant. The news elates Sid, who Mel later reveals cannot conceive a child.
In a dusty small town, Mel and Bobbie begin to sell off the stolen narcotics out of a rundown motel. A group of armed rednecks attempt to steal their stash, Mel and Bobbie are shot during the altercation, but Bobbie and Sid manage to kill the four men and take their money. The group flee to the home of the Reverend, a preacher and illegal arms dealer from whom Mel acquires his guns. The Reverend allows them to stay at his home, but only in exchange for half of their haul.
After Mel and Bobbie recover, the group continue their illegal exploits, uniting with Jewels, a flamboyant gay criminal with whom Mel has worked in the past. Mel, Bobbie, and Sid agree to commit a robbery with Jewels, but Rosie is reluctant, shaken by Mel and Bobbie's near-death incident. The night before the planned robbery, Rosie commits suicide by overdosing on heroin in their motel. A devastated Bobbie keeps Rosie's death a secret, and goes along with Mel and Sid in the morning to the home of the wealthy couple Jewels has planned for them to rob.
When they arrive, they discover Jewels already inside, beating the male occupant after having tied up his wife. The robbery quickly goes awry, and Bobbie shoots Jewels through the throat, killing him. Mel, angered that Bobbie has killed their cohort, proceeds to murder the homeowners to prevent being identified to police. Bobbie, Mel, and Sid flee with $80,000, but Mel is infuriated by Bobbie's actions.
During the car ride, Bobbie reveals that Rosie is dead and her body is back at the motel, which causes Sid to have a breakdown, as she has developed a maternal relationship with both Rosie and Bobbie. While stopping for gasoline, Mel insists they murder Bobbie to conceal their crime, which Sid reluctantly agrees to when Mel threatens her life as well. Bobbie goes to use the restroom, and Sid follows, tearfully warning him that Mel plans to murder him. She gives him a stack of money and pleads for him to go. The two embrace, and Bobbie flees through a cornfield. When Mel realizes Bobbie has escaped, he looks into the field to kill him, but is unable to spot him. Mel punches Sid in the face as punishment for her betrayal, then drives off as Bobbie continues to run.
