Dexter and Emma spend the night together following their graduation from Edinburgh University, in 1988. They talk about how they will be once they are 40. While they do not become romantically involved completely, this is the beginning of their friendship. The novel visits their lives and their relationship on 15 July in successive years in each chapter, for 20 years.
Emma wants to improve the world, and begins writing and performing plays, which remain unsuccessful, while Dexter travels through the world, drinking and hooking up with women. Eventually both move to London, where Emma becomes a waitress in Kentish Town, at a Tex-Mex restaurant, while Dexter becomes a successful television presenter.
While there are various attempts from both sides to start a relationship, coincidences stop Emma and Dexter from getting together, and while they have relationships with other people, they remain best friends, each secretly longing for the other. They are drawn closer through a holiday together and the death of Dexter's mother.