The City of London, 1678. NewYear's Day. London is gripped by hysteria, and rumours of Catholic plots and sinister foreign assassins abound. When the body of a young boy drained of his blood is discovered on the snowy bank of the Fleet River, Robert Hooke, the Curator of Experiments at the just-formed Royal Society for Improving Natural Knowledge, and his assistant Harry Hunt, are called in to explain such a ghastly finding - and whether it's part of a plot against the king. They soon learn it is not the first bloodless boy to have been discovered.