Autumn, 1671: war looms with Holland, while discontent grows with England's dissolute monarch, Charles II, grows. Meanwhile Betsy Brand, celebrated actress with the Duke's Theatre, has a predicament. Beset by financial troubles, she is obliged to leave London and undertake a dangerous venture as a spy for her country. What starts out as a fact-finding mission to the Low Countries soon turns into a deadly game, in which Betsy must use all her acting skills. Though she meets her match in Captain Mullin, a reckless fellow-agent, the two find they must work together to confront an unseen killer, and unravel a plot that strikes at the very heart of England itself...