Newly divorced Jo is delighted to move into her best friend's spare room. The high-tech luxury flat is managed by a meticulous Home Assistant, Electra. Late one night, Electra says one sentence that rips Jo's fragile world in two: "I know what you did." And Jo is horrified. Because in her past she did do something terrible. Something unforgivable. Now she wants to destroy you. Terrifyingly believable and utterly gripping.