England, 1979. Vincent, Lawrence and William are the last remaining residents of a secluded New Forest home, part of the government's Sycamore Scheme. Every day, the triplets do their chores, play their games and take their medicine, under the watchful eyes of three mothers: Mother Morning, Mother Afternoon and Mother Night. Their nightmares are recorded in The Book of Dreams. Their lessons are taken from The Book of Knowledge. And their sins are reported in The Book of Guilt. All the boys want is to be sent to the Big House in Margate, where they imagine a life of sun, sea and fairground rides. But, as the government looks to shut down the Sycamore Homes, the triplets begin to question everything they have been told.