Claire Roget becomes the new head clinical psychiatrist at Greatbach Secure Psychiatric Unit outside Stoke-on-Trent, England, after the previous doctor, Heidi Faro, is savagely murdered by a patient.

Heidi (Emma Bulger) is a Swiss orphan being cared for by an aunt who, when offered a position as a domestic in the city, ships the girl off to live with her grandfather.

Although she's finally turning thirteen, Heidi is otherwise having a difficult summer: her mother is expecting a baby, meaning the family won't be going away for their usual visit to Heidi's beloved grandmother; her best friend keeps asking Heidi to go swimming, but she's become afraid of the water; her father is facing increased ostracism for working as a "border crosser" in the wealthier Western part of the city.