Clearly influenced by the darker, more sinister style of spaghetti westerns, Dirty Little Billy offers a unique insight into the beginnings of the notorious outlaw Billy The Kid.

A young American soldier, rendered in pseudocoma from an artillery shell from WWI, recalls his life leading up to that point.

Cal Thacker, a would-be artist, shares his slum living quarters with Mike Rubel, a pusher who exists in a private drug-centered world, and Richard Stoney Morgan, an embittered drifter who sponges from the other two. Cal's girl friend, Carrie, who has provided his only meaningful human contact, finds him in bed with another girl and breaks up with him. In despair, Cal tries unsuccessfully to obtain funds by selling his paintings. His motorcycle is wrecked in a crash, though Cal miraculously escapes injury. Later in the day, the three roommates meet at the apartment and attempt to obliterate their problems with cheap whiskey. The liquor only creates new problems, however; Mike and Cal become involved in a violent argument with Stoney, who eventually leaves. Seeking revenge, Stoney reports Mike to the police as a marijuana pusher and then returns to the apartment with a knife. In the fight that ensues, Cal kills Stoney; but Cal is then gunned down by police.