Summary of plot
Christina and Christopher were moved apart aged fifteen, when their father took Christopher to live with him in a cabin on the lakes in Canada and sent Christina to live with her grandparents on their mother's side. They have never known their mother, who died in childbirth, never knowing she was carrying twins.
As adults, they are both dissatisfied with their lives. Christina tells her story in the first person, in the present tense, interspersed with third person narration in the past tense, wherever or whenever she is absent from the action.
Christina, known as Tina (which she dislikes), feels trapped in her marriage and finds it a struggle to bring up her lively six-year-old girls. Although she loves her husband, Iain, and their daughters, she wishes she were as free as when she had been an art student before she met Iain. She wants to paint but does not have the money or the time to do what she craves. She is grieving the recent loss of her beloved dog and has become seriously depressed. She has blanked out the death of her baby who was born prematurely and did not survive long. She starts going for art therapy and exposes the truth about a fire in her early childhood for which she has always felt guilty.
Christopher, known as Chris, has enjoyed being in Canada and loves his job as a pilot of small planes and his intermittent work as a radio journalist. However, since early childhood he has felt that he is female within a male body and, after a love affair that petered out, he would like to have gender re-assignment. He approaches the director of a pioneering animal research clinic and is offered a whole body swap, with a transplant into the body of a young woman who has lain in PVS for many years. Fortuitously, his radio station sends him to do a story on the animal transplants to look for illegal activities and cruelty. He uses this as a cover to go with Tina to revisit childhood haunts, planning to fake an accident so that he can have his transplant and emerge as a woman, while his male body is declared dead, and Tina can return to her family.
A maverick neurosurgeon at the clinic, with complete disregard for Christopher's wishes, decides to swap Tina and Chris.
Christopher, in Tina's body, is sent to a Coma Care Centre near Tina's home and kept in an induced coma for a year. Her husband and family have no reason to doubt that this is Tina.
Christina, now Chris, is told her female body has been cremated and is then released from the research clinic to live as a man. She has an implanted tracking device in order to be kept under surveillance. Thinking of herself as Uncle Chris, part female and part male, and not wishing to go back to her family, she sets out to explore her new body and develop a new way of life. After a year, she badly misses her husband and daughters, and finds out that her female body is not dead. She recovers the memory of her baby who died and decides to go home.
Christopher awakens and discovers that he has been duped by the research clinic. Brother and sister are re-united and realise they have been swapped. They decide to keep this secret, as each of them prefers their new lifestyle.
Their mother-in-law has been looking after the children and as an extended family unit of husband and wife, children, uncle and grandmother, they live together in moderate harmony.
They learn to sail and after trial runs, set off across the channel. Chris is overwhelmed by a previously unrecognised passion for Iain, who is now unattainable as a sexual partner. The sailing is going well until they are nearly run down by a tanker. Chris and the twins fall overboard.
Chris is rescued by the research clinic and hits an all-time low, believing everyone is lost, not knowing the girls are also in the clinic and that Iain and Tina are OK. Iain and his mother are also at rock bottom, believing they have lost Chris and the girls, and disliking each other.
At Tina's suggestion, her husband and his mother seek out the art therapist and uncover some uncomfortable truths about his childhood.
The research clinic releases Chris and the children, and everyone is re-united once more. They work out new living arrangements. Gradually Chris is reconciled to living with a husband who is no longer hers. She has her family around her, and her art, and that is what truly matters.