One long, hot summer in seventies London, Holly and Marina make a childhood pact to be friends forever. For the troubled, unpredictable Marina, with her seemingly glamorous father and her Valium-addicted mother, Holly stays the only constant in a life of divorcing parents, experimental drugs and fashionable self-destruction. Meanwhile, Holly buries herself in books out of feelings of frustration with her over-protective mother and a nagging insecurity around her beautiful and possessive best friend. She holds just one secret from Marina, her increasing passion for Marina's brother Nat. As the years roll by, the girls experience everything life has to offer, sex, love, loss and rock 'n roll. But eventually for Holly, a friendship which has never been equal gradually begins to feel like a trap.