S has disappeared from Ruth and Leonard's home in Brighton. Suicide is suspected. The couple, who had been spying on their young lodger since before the trouble, begin to pour over her diary, her audio recordings and her movies - only to discover that she had been spying on them with even greater intensity. As this disturbing, highly charged act of reciprocal voyeurism comes to light, and as the couple's fascination with S comes to dominate their already flawed marriage, what emerges is an unnerving and absorbing portrait of the taboos, emotional and sexual, that broke behind the closed doors of 1950s British life.