A conscientious Treasury official is murdered in Westminster, and the Earl of Clarendon quickly identifies another clerk as the likely culprit. Thomas Chaloner distrusts the convenient solution and begins examining the office's accounts, routines and private alliances.
His enquiries reveal a lucrative network of corruption protected by men who expect the machinery of government to conceal their theft. Poisoning becomes both a method of murder and a warning to potential witnesses, leaving Chaloner to expose the scheme before another official is silenced and the innocent suspect is condemned.