Colm Lowe is an artist, a watercolourist, specialising in birds. His life with his wife, Maggie, changes when he moves from London’s suburbs to a house in Devon overlooking the Exe estuary. It changes even more, and not for the better, when Maggie’s father, Jack, a widower, comes to live with them. Struggling under the pressures of caring for Jack, Maggie and Colm begin to see each other differently. Cracks appear in their marriage. When Jack asks Colm to help him die, Colm glimpses freedom and decides to oblige by leaving Jack to drown in the bath. But it’s not that simple. Mercy killing, practised without a manual, is not an exact science.