London, 1985. Joe, father to 11-year-old Matty, has disappeared and nobody will explain where he's gone, or why. In the long, hot summer that follows, Matty's hunt for Joe leads to the ponds at Hampstead Heath. Beneath the water, there is a new kind of freedom. Above the water, a welcoming community of men offer refuge from an increasingly rocky home life. Fourteen years later, a new revelation sees Matty set off alone in a campervan, driving westwards through Ireland, swimming its wild loughs and following the scant clues left behind about Joe. The trip takes a dangerous turn, and Matty is forced to rely on the kindness of strangers. But safety comes at a price, and with desire and fear running high, the journey turns into an explosive, heart-rending reckoning with the past.