Elisa Brown is driving back from her annual visit to her son Silas's grave. The road is flat and featureless, and so she finds herself focussing on an old crack in her windscreen. For a moment, she loses sense of all else around her.

When she comes back to herself, everything has changed.

The car she is driving is not the same car. Her body is more subtly changed. She's wearing different clothes. But a name badge pinned to her blouse tells her she's still Elisa Brown. When she arrives home, her life is familiar, but different. There is her house, her husband. But in the world she now inhabits, Silas is no longer dead, and his brother is disturbingly changed. Elisa has a new job, and her marriage seems sturdier, and stranger. Has she had a psychotic break? Or has she entered a parallel universe? She soon discovers that these questions hinge on being able to see herself as she really is, something that might be impossible for Elisa or for anyone.