As the story begins, the main character, Tom Crick, is remembering childhood in eastern England. His thoughts return to the present, and we learn that he has lost his job teaching history because the school is closing its history department and because Tom's wife has committed a crime.
The plot flashes back and forth from the past to the present, all having to do Tom and his wife, Mary. Tom remembers finding a friend's drowned body, and Mary telling him that Tom's brother Dick had killed the man. It is plausible for the reader to suspect Mary.
While remembering the past and living in the present, Tom tells about the history of his family, his relationship with Mary, the story of his grandfather, and the usefulness of history. He describes trying to get Dick to confess to the murder, but failing. Mary decides to teach Dick, who is mentally disabled, all about sex, and when she becomes pregnant, she tells Tom she's not sure whether he is the father or whether it was Dick or their dead friend Freddie! Later in the story, we will learn that she aborted this baby.
In the present, Mary announces at the age of 52 that she is pregnant. However, when Tom comes home one day, he discovers that she has stolen a baby. He insists that they return the baby, and Mary is placed in a mental hospital.
There is a side story about Dick's having been conceived in incest, and the story ends with him committing suicide.
Whew! This story is hard to keep up with!