Who claims that he is a loner?
Preparatory 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.
Martyn