Each summer a group of families holiday together in St. Ives, Cornwall, but in 1972 their lives are shattered and they never meet up again. In a lane in the village of Zennor a hotel night porter is found fatally poisoned. Later that same week the body of another man is washed ashore.

Grant Morrison, then aged seventeen, had long been troubled by the two deaths and their aftermath and, decades later, decides that the time has come to uncover the truth. He and his wife travel from London to Cornwall, and he explains how five of the holidaymakers had been questioned by the police, including a family friend called Richard who had an affair with his mother in the 1970s, but that no one was charged. On a coastal walk the couple have the uneasy sense they are being followed.