In Fingersmith, by Sarah Waters, something very unexpected happens. It happens at the end of Part One, after six chapters, about one-third of the way through the novel, and it turns everything upside down. We had thought that Sue Trinder, our narrator, was part of a plot to cheat an heiress out of her fortune by having her committed to a mental asylum, but in fact the heiress, Maud, was also part of a plot, of which we knew nothing, to have Sue locked up in the madhouse. The scene in which Sue travels to the asylum with her partner in crime Richard to commit Maud, only to be handed over herself to the doctors by Richard and Maud, presents one of those absolutely unpredictable moments on which mystery fiction turns: an unexpected event that arrives from the future, which cancels everything we had thought to be the case and replaces everything we expected to happen.

But does it arrive from the future? Its unexpectedness is organised by the perspectival structure of the novel and by the distribution of information that this structure entails, because we only know what Sue knows, and access to information possessed by other characters is withheld. It is true that, as we read through Part One, the asylum event has not happened yet, but its unexpectedness is the function of what we do not yet know more than it is the function of what has not yet happened.