Maggie moves to Brighton after splitting up with her long-term boyfriend, and, unable to find a job, starts work as a lapdancer. Failing to make any new friends, she writes letters compulsively, and the highlight of her day is the sound of the morning post being delivered. Maggie gradually becomes obsessed with the married couple, Libby and David, living next door. Libby has given up work after having a baby, and is finding life as a full-time mother very difficult. Just as she persuades David that she should return to work, he is asked to take a sabbatical from his management-consultant job. He's always longed to travel, and convinces Libby that they should spend six months in Cuba, learning Spanish. Maggie, deciding she too wants to travel, follows them to Havana, where the horrors of her past - in particular her young sister's violent death - begin to haunt her. And as Maggie starts to break down, she tries to take over Libby's life...