Private school student Liz resurfaces, disheveled and bloody, after disappearing 18 days prior along with her peers Mike, Geoff, and Geoff's girlfriend, Frankie. Liz is interviewed by a psychiatrist, Dr. Phillipa Horwood. Liz recounts how her friend Martyn arranged for the four to spend the weekend in an abandoned underground nuclear fallout shelter to avoid a school field trip. Liz portrays herself as being unpopular but as Frankie is her friend, she was able to convince the others to go down into the shelter. When Martyn fails to return for them, the four belatedly realize they are trapped, and begin to turn on one another. They discover hidden microphones in the shelter which were placed there by Martyn. Attempting to get Martyn's attention, Frankie pretends to be ill, while Mike and Liz feign hatred for one another; Martyn has had unrequited romantic feelings for her since their childhood. Liz claims they woke up one morning and found the hatch opened, allowing them all to finally escape. Phillipa is skeptical of Liz's story. Martyn is subsequently taken into police custody, where he tells an entirely different story: He claims Liz and Frankie orchestrated the scheme in order for Liz to get to know Mike better, and for Frankie to spend time with Geoff. Liz is not the unpopular loner she has portrayed herself as, in fact it is Martyn who is the loner while Liz and Frankie are the popular girls. Meanwhile, Liz returns home, where she experiences disturbing flashbacks about what happened. An enraged Martyn goes to visit Liz, believing she is framing him. She runs from him through the garden and approaches a weir. Martyn cries, and Liz hysterically says that she knew they would let him go because they could not prove anything. At their next meeting, Liz tells Phillipa that she cannot remember what happened in the shelter. Phillipa decides to bring her there, hoping to invoke her memory. Once inside, Liz reveals the truth: She had locked herself and her friends inside in the hopes of winning Mike's affection, with whom she was obsessed. After discovering that both he and Geoff had slept with Frankie, she spontaneously decided to lock the door, isolating them and giving her the opportunity to become closer to him. Initially, the four had planned to drink and do drugs in the shelter, but the realisation that they were unable to escape initiated the group into hysteria. Frankie soon becomes ill and is unable to stop vomiting, this increases her dehydration, tears the lining of her stomach and puts a great strain on her heart. This causes cardiac arrest and Frankie dies. Liz, Mike, and Geoff gradually ran out of food and water. When Mike discovered that Geoff was hoarding a Coca-Cola can in his backpack, he attacks him in a fit of rage but accidentally kills him from beating Geoff's head repeatedly on the floor. Liz suggested a suicide pact, where upon Mike professed his love for her; this prompted her to climb the ladder toward the shelter's entrance and unlock the door. When Mike discovers she had the key all along, he attempts to chase after her, but falls to his death from the ladder. After Liz finishes recounting the story to Phillipa, Phillipa asks her to make an official statement corroborating Martyn's version of events; Liz refuses, having murdered Martyn when he visited her at her home the day prior. Police arrive at the shelter, and Liz begins screaming for help, pretending Phillipa was attempting to hurt her. Meanwhile, Martyn's corpse is fished out of the river; in his pocket, police find the key to the shelter, which implicates him in the events. The police attribute his death to suicide. Liz is allowed to go free. She leaves the shelter in the back of an ambulance, smirking at Phillipa from the window as it drives away.
Nick Hamm began casting actors at the end of 1999. Hamm described newcomer Keira Knightley as a young version of Julie Christie. To prepare for the role, Thora Birch visited an English public school. Principal photography began in 2 July 2000 and ended on 9 November 2000 lasted six weeks and took place around London and southern England. Specific locations included Downside Boarding School in Somerset and Bray Studios. The film was shot in Super 35 format.
Reception
The film received mixed reviews. On Rotten Tomatoes, the press's critics gave 50% positive reviews. Michael Thomson, in a review for the BBC, said the film was a "dark, grisly adventure" influenced by William Golding's novel Lord of the Flies, with the hole substituting for the island setting. He criticized the camerawork and some of the dialogue, but praised Thora Birch.
