An Autumn in Araby opens in Suffolk (1869), where Suzanna Copley has just arrived to take charge of widower's Justin Ormerod's uncontrollable young son, Rupert. But she soon realises that Castle Delamere holds far greater dangers than the tantrums of one small boy, and as she befriends him she learns that he is more in need of protection than discipline.

When her employer announces that he has been commissioned to paint scenes commemorating the opening of the Suez Canal, and that Suzanna and Rupert are to accompany him on the long sea voyage to Egypt, she is delighted, believing that they can leave fear and trouble behind. She cannot know that a murderer is tracking their footsteps and will be aboard the SS Hindustan, too, watching and waiting for an opportunity to kill the child who has unwittingly become an instrument of revenge.