In Barrington House, an upmarket block in London, there is an empty apartment. No one goes in and no one comes out, and it's been that way for 50 years, until the night a watchman hears a disturbance after midnight and is drawn to investigate. What he experiences is enough to change his life forever. Soon after, a young American woman, Apryl, arrives at Barrington House. She's been left an apartment by her mysterious Great Aunt Lillian who died in strange circumstances. Rumors claim Lillian was mad, but her diary suggests she was implicated in a horrific and inexplicable event decades ago. Determined to learn something of this eccentric woman, Apryl begins to unravel the hidden story of Barrington House. She discovers that a transforming, evil force still inhabits the building, and that the doorway to Apartment 16 is a gateway to something altogether more terrifying.