The Last House on the Left

Mari Collingwood plans to attend a concert with her friend Phyllis Stone for her 17th birthday. Mari's parents, Estelle and John, express concern about her friendship with Phyllis, but they 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 while trying to buy marijuana. He leads them to an apartment where the criminals trap them. 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.
The following day, Mari and Phyllis are bound, gagged, and put in the trunk of Krug's car and transported to the woods. Mari recognizes that the road is near her home. Phyllis is forced to urinate in her jeans, and Mari and Phyllis are forced to perform sexual acts on each other. Phyllis distracts the kidnappers to allow Mari to escape, but is chased by Sadie and Weasel, while Junior stays behind to guard Mari. Mari tries to gain Junior's trust by giving him her necklace and calling him "Willow." Phyllis stumbles across a cemetery where she is cornered and stabbed by Weasel. She crawls to a nearby tree and is stabbed to death. Mari convinces Junior to let her go, but Krug halts her escape. Krug carves his name into her chest, then rapes her. Mari vomits, quietly says a prayer, and walks into a nearby lake, where Krug fatally shoots her.
After they change out of their bloody clothes, the gang goes to the Collingwoods' home, masquerading as traveling salesmen. Mari's parents let them stay overnight. The gang finds photos of Mari and realizes it is her home. Later, when Junior is amid heroin withdrawal, Estelle enters the bathroom to check on him and sees Mari's peace symbol necklace around his neck. She finds blood-soaked clothing in their luggage and overhears them talking about Mari's death and her disposal in a nearby lake.
Estelle and her husband rush into the woods, where they find Mari's body and decide to take revenge. Estelle pretends to seduce Weasel, performs oral sex on him, bites off his penis, and leaves him to bleed to death. John takes his shotgun and shoots at Krug and Sadie. Krug escapes into the living room and overpowers John. Before Krug can kill John, Junior enters with a gun and threatens Krug, attempting to save John's life. Krug manipulates Junior, who is distraught and going through withdrawal from heroin, into killing himself with the gun instead. Using the distraction, John picks up a chainsaw from the basement and approaches Krug. Sadie enters with the switchblade and tells Krug to take the back door to escape, but Krug is hindered by an electrocution booby trap. Sadie, now terrified of both Krug and John, runs outside. After a scuffle between her and Estelle, she falls into the backyard swimming pool, where Estelle slits her throat. The sheriff arrives just as John kills Krug with the chainsaw.
Covered in blood, the cops and parents somberly overlook the chaos.