Becca and her sister, Rosaline, have forged ahead with family lives and careers, growing distant through time and circumstance. But when the body of an older woman is discovered at sunrise on Laxey Beach in the Isle of Man, it brings devastating news for the sisters.

A veteran beat cop and teenage girl fall to their deaths from a tower block in south-east London, leaving a five-year-old boy and rookie police officer Lizzie Griffiths on the roof, only for them to go missing. Detective Sergeant Sarah Collins is drafted in to investigate, working to find Lizzie before she comes to serious harm, but also to uncover the truth behind the grisly tower block deaths.