It is the summer of 1887 and everyone is looking forward to Queen Victoria's Golden Jubilee. Young police constable David Price's greatest concern is how much drunken disorder he and his colleagues will have to deal with. This changes when he is part of a force sent to a Lascar hostel on the docks, to break up a disturbance. The constables arrive to find that trouble hasn't even started. Close to the scene, David discovers an intricate mechanical rat, which is taken from him by a mysterious woman. He discovers she is a socialite, a friend of the royal family, and the eldest daughter of an Indian rajah.
Tracking the princess down to her Richmond home provides the young officer with some answers. Many more questions arise. He finds himself embroiled in a deadly plot to raise racial tensions, set to culminate in a major incident that will rock the capital. Worse, David realises some of his own colleagues are involved. He has no idea who he can trust...