The murder of a man in broad daylight on London Bridge is the first indication that the Earl of Clarendon's fears of a rebellion against the newly restored monarchy may be well-founded. His spy, Thomas Chaloner, suspects the assassin may be a member of a group dedicated to seeing the return of Puritanism, and at the same time he learns of a faction close to the King determined to bring back the old ways of the Roman Catholic Church. He discovers, too, that the killing on the Bridge is not the only assault committed there recently, and begins to decipher a link between the violence and the people who manage the Bridge and its tottering, ramshackle buildings. As he moves unobtrusively between White Hall, the elegant mansions along the Strand and the heaving congestion on the only river crossing he becomes aware of an undercurrent of restlessness in the capital. And it soon becomes clear that the groups he is investigating are planning some extraordinary climax to achieve their separate aims on Shrove Tuesday, which gives him very little time to identify the ring-leaders and thwart their intentions ...