Elspeth dies, leaving her entire estate to the identical twin daughters of her own identical twin sister. The condition of inheritance is that the young women must live in Elspeth's flat in London, leaving their parents behind in Chicago, for an entire year. The twins' close relationship with each other is tested as they explore their new surroundings and meet their two neighbours, Elspeth's former lover Robert and the reclusive Martin who suffers from OCD. Meanwhile, Elspeth's ghost begins to haunt her former home.
That's a bare-bones description of the plot, because I don't want to give away too much of what takes place in this novel. To be honest, though, I'm not sure if I can recommend this weird gothic story too heartily; it seemed to lack essential character development which would have helped the characters' actions to make sense. Also, the setting of this story features a real Victorian cemetery in London and apparently Niffenegger spent a lot of time there doing research; this has led to a few unfortunate passages which are basically just research dumps about the cemetery and the people buried there. Aside from those parts I can say that this is a very nicely written novel; I particularly appreciated Niffenegger's compassionate treatment of Martin and her exploration of his efforts to live with his crippling mental illness. On the whole, though, I felt dissatisfied when I finished the book and wouldn't read it again.