A pair of teenage girls are headed to a rock concert for one's birthday. While trying to score marijuana in the city, the girls are kidnapped by a gang of psychotic convicts.
Mari Collingwood plans to attend a concert with her friend, Phyllis Stone, for her 17th birthday. Her parents, Estelle and John, express concern both at the band and Mari's friendship with Phyllis, but let her go after giving their daughter a peace symbol necklace.
Phyllis and Mari go to the city for the concert. On the way, they hear a news report on the car radio of a recent prison escape, involving criminals Krug Stillo, a rapist and serial killer, his 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 stroll the streets, seeking someone who might sell them marijuana. They find Junior, who leads them back to an apartment, where they are immediately trapped by the criminals. Phyllis tries to escape, then tries to reason with the criminals, but fails and is gang-raped by Krug, Weasel and Sadie.
Meanwhile, Mari's unsuspecting parents prepare a surprise party for her.
Both Mari and Phyllis are transported to the woods by the criminals. Mari recognizes that the road is near her home. Mari and Phyllis are forced to have sex with each other and then Sadie performs oral sex on a weeping Mari. Phyllis runs away to distract the kidnappers and offer Mari an opportunity to escape, but is chased by Sadie and Weasel, while Junior stays behind to guard Mari.
While the two criminals chase Phyllis, Mari tries gaining Junior's trust by giving him her necklace as a symbol of her trust and naming him "Willow".
Phyllis manages to hit Sadie in the face and runs, but is then cornered and stabbed to death by Weasel. Sadie reaches into Phyllis's wounds and pulls out the insides.
Mari eventually convinces Junior to let her go, but they are immediately halted by Krug. Sadie and Weasel present Phyllis' severed hand and half forearm and Krug proceeds to carve his name into Mari's chest. As Mari screams in pain, Krug then rapes her. Soon after this act, Mari vomits. Mari quietly says a prayer then walks into a nearby lake. Krug shoots Mari and she floats on the top of the lake. Krug, Sadie, and Weasel wash and change out of their bloody clothes.
In their new attire, the gang go to the Collingwoods' home, masquerading as travelling salesmen. Mari's parents agree to let them stay overnight. Junior exposes their identity when Mari's mother, Estelle, sees Mari's peace symbol necklace dangling around his neck. Later that night she listens in to the gang while they are spending the night in Mari's bedroom and finds blood-soaked clothing in their luggage. She and Dr. Collingwood rush out into the woods, where they find Mari's body on the bank of the lake. They carry Mari's body back into the house then exact revenge against the crooks.
Outside, Estelle seduces Weasel and then performs fellatio on him which turns deadly when she bites off his penis and leaves him to bleed to death. Inside the house, Dr. Collingwood carries his shotgun into his daughter's bedroom, where two of the criminals are sleeping.
Krug escapes into the living room and overpowers the doctor, but the criminal is then confronted by Junior, who now brandishes a firearm and threatens to kill him. However, his father is able to manipulate him and Junior commits suicide.
Sadie rushes outside where she is tackled by Estelle. The two of them wrestle and fight on the ground. Estelle eventually is able to slit Sadie's throat with a knife and Dr. Collingwood kills Krug with a chainsaw. After the bloodbath, the couple meets in the living room as the police come.
Click here to read Roger Ebert's review.Source: Wikipedia