The year is 1666.
"The death of a well-connected physician, the mysterious sinking of a man-of-war in the Thames and the disappearance of a popular courtier are causing concern to Thomas Chaloner's employer. When instructed to investigate them all, he is irritated that he is prevented from gaining intelligence on the military preparations of the Dutch. Then he discovers common threads in all the cases, which seem linked to those planning to set a match to the powder keg of rebellion in the city."