In the garden of a large Georgian villa in Southwest London, socialites and politicos swap gossip and sip Pimm's. Not far from this frivolity, though, a body has been discovered in the River Thames. At first, it appears to be an unfortunate accident, but the death is connected to this gathering of who's who in a way that may spell scandal. Meanwhile, Detective Inspector Caius Beauchamp, attempting to enjoy an evening at the theater, is shocked to discover another dead body just a few seats away. The death is linked to the decades-old disappearance of a 14-year-old girl at a boarding school in Cornwall. If Caius wants the resources to solve the tragic mystery of the girl's disappearance, he will have to take new orders from a shadowy government minister who contends that the accidental drowning in the Thames was anything but.

Rupert's 30th birthday party is a black-tie dinner at the Kentish Town McDonald's --- catered with cocaine and expensive champagne. The morning after, his girlfriend Clemmie is found murdered on Hampstead Heath, a single stiletto heel jutting from under a bush. All the party-goers have alibis. Naturally. This investigation is going to be about aristocrats and Classics degrees, Instagram influencers and whose father knows who. Or is it "whom"? Detective Caius Beauchamp isn't sure. Sharply dressed, smart and thoroughly modern, he discovers Clemmie's body on his early morning jog. As he searches for the dark truth beneath the luxurious life of these London socialites, a wall of staggering wealth and privilege threatens to shut down his investigation before it's even begun.