In the mid 1970s, Alice Lamb, a reclusive writer, lives by the seaside in a small town in Kent where she is bullied by local children and viewed as a witch. She has lived in the village since the 1940s.
During WWII, as part of the war effort, she is entrusted with the care of a young boy, Frank, who has come from London where it is unsafe. Though Alice does not want to care for him as she fears it will interfere with her work, she reluctantly lets him stay believing that he has nowhere else to go and she will be able to be rid of him a week.
Reluctantly bonding with Frank, she begins to remember her previous connection with Vera, a young writer who she met and fell in love with during her university days. Despite becoming lovers, Vera ultimately decides to leave Alice, not because their relationship is taboo but because she has a strong desire to be a mother which Alice doesn’t understand.
Alice and Frank begin to bond after he takes an interest in her scholarly work and she explains Fata Morgana mirages to him. However at the end of their week together she is still willing to let him go. Alice changes her mind and decides to keep Frank on after learning that moving him to a new family will require him to move to another village.
The day before Frank’s birthday Alice is informed that his father has died. As Alice was similarly devastated by the loss of her own father she decides to delay telling Frank. Preparing a permanent room for Frank to stay in Alice is shocked to discover photographs of Frank with his mother, who is shown to be Vera. At the same time Frank discovers his father has died and runs away to be with his mother in London. Alice chases after him and the two arrive in time to see his home in flames after a bombing.
On their way home Frank runs away to the sea and nearly drowns. He is rescued by Alice. Returning to Alice’s home they are met by Vera, who was away from home at the time of the bombing. Vera confesses to having engineered Frank and Alice’s meeting.
In the 1970s Alice’s writing is interrupted by Vera, who has continued to live with her since their reunion. The two walk on the beach and are joined by an adult Frank who has come to visit his two mothers.