Mari Collingwood plans to attend a concert with her friend, Phyllis Stone, for her seventeenth birthday. Her parents, Estelle and John, express their concern about her friendship with Phyllis, but let her go and give her a peace symbol necklace. Phyllis and Mari head into the city and on the way, they hear a news report of a recent prison escape involving criminals Krug Stillo, a sadistic rapist and serial killer; his heroin-addicted son, Junior; Sadie, a promiscuous psychopath and sadist; and Fred "Weasel" Podowski, a child molester, peeping Tom, and murderer. Before the concert, Mari and Phyllis encounter Junior when trying to buy marijuana. He leads them to an apartment where they are trapped by the criminals. Phyllis tries to escape and reason with them, but she fails and is gang-raped. Meanwhile, Mari's unsuspecting parents prepare a surprise party for her.