The Great Spa sits on the edge of London, a structure visible from space. The power of Britain on the world stage rests in its monopoly on "The Treatment," a medical procedure which transforms the richest and most powerful into a state of permanent physical youth. The Great Spa is the place where the newly young immortals go to revitalise their aged souls.

In this most secure of facilities, a murder of one of the guests threatens to destabilise the new order, and DCI Oates of the Metropolitan police is called in to investigate. In a single day, Oates must unravel the secrets behind the Treatment and the long-ago disappearance of its creator, passing through a London riven with disorder and corruption. As a night of widespread rioting takes hold of the city, he moves towards a climax which could lead to the destruction of the Great Spa, his own ruin, and the loss of everything he holds most dear.