The Virgin Suicides

The story takes place in the suburbs of Grosse Pointe, Michigan during the mid-1970s, as a group of neighborhood boys, now grown men acknowledging in voice-over (narrated by Giovanni Ribisi who speaks for the group as a whole) reflect upon their memories of the five Lisbon sisters, ages 13 to 17. Unattainable due to their Catholic and overprotective, authoritarian parents, math teacher Ronald (James Woods) and his homemaker wife (Kathleen Turner), the girlsâTherese (Leslie Hayman), Mary (A. J. Cook), Bonnie (Chelse Swain), Lux (Kirsten Dunst), and Cecilia (Hanna R. Hall)âare the enigma that fill the boys' conversations and dreams.
The film opens in the summer with the suicide attempt of the youngest sister, Cecilia, as she slits her wrist in a bath. After her parents allow her to throw a chaperoned basement party intended to make her feel better, Cecilia excuses herself and jumps out of her second story bedroom window, dying when she is impaled on an iron fence below. In the wake of her act, the Lisbon parents watch over their four remaining daughters even more closely. This further isolates the family from the community and heightens air of mystery about the girls to the neighborhood boys in particular.
At the beginning of the new school year in the fall, Lux forms a secret and short-lived romance with Trip Fontaine (Josh Hartnett), the school heartthrob. Trip comes over one night to the Lisbon residence in hopes of getting closer to Lux and watches television with the family. Soon Trip persuades Mr. Lisbon to allow him to take Lux to the upcoming Homecoming Dance by promising to provide dates for the other sisters, to go as a group. After winning Homecoming king and queen, Trip persuades Lux to ditch the group and have sex on the school's football field. Afterwards, Lux falls asleep on the grass, and Trip, becoming disenchanted by Lux, abandons her. At dawn, Lux wakes up alone and has to take a taxi home.
Having broken curfew, Lux and her sisters are punished by a paranoid Mrs. Lisbon by being taken out of school. Unable to leave the house, the sisters contact the boys across the street by using light signals and sharing songs over the phone.
During this time, Lux rebels against her repression and becomes promiscuous, having anonymous sexual encounters on the roof of her house late at night; the neighborhood boys spy and watch Lux from across the street. After weeks of confinement, the sisters leave a note for the boys. When the boys arrive that night, they find Lux alone in the living room, smoking a cigarette. She invites them inside to wait for her sisters, while she goes to start the car.
Curious, the boys wander into the dark basement after hearing a noise and discover Bonnie's body hanging from the ceiling rafters. Horrified, they rush back upstairs only to stumble across the body of Mary in the kitchen. The boys realize that the girls had all killed themselves in an apparent suicide pact: Bonnie hanged herself; Mary died by putting her head in the gas oven; Therese took an overdose of sleeping pills and Lux died of carbon monoxide poisoning when she left the car engine running in the garage.
Devastated by the suicides of their children, Mr. and Mrs. Lisbon leave the neighborhood. Mr. Lisbon has a friend clean out the house and sell off the family belongings in a yard sale. Whatever didn't sell was put in the trash, including the family photos, which the neighborhood boys collect as mementos. The house is sold to a young couple from the Boston area. The adults in the community go about their lives as if nothing happened. The boys do not forget about the girls. As the film closes, the men acknowledge in voice-over that they had loved the girls, and that they will never know why the Lisbon sisters took their lives.

Question: Who is having sex on there roof late at night?
Answer: Lux