Detective Superintendent Grace O’Malley of London’s Metropolitan Police receives a dubious phone call. A self-proclaimed witch hunter --- using the alias of Matthew Hopkins, the notorious 17th-century witchfinder general --- is leading her to his first victim. Someone is exploiting the bloody history of the witchfinder to start a modern-day witch hunt, making sure their debut murder of a TV medium is broadcast worldwide during Halloween night on Westminster Bridge. The clock is ticking for this high-profile case. Grace needs to find out who is behind the premeditated crime before the witch hunter can strike again. But the more she investigates, the more she finds herself in an intricate web of lies, deceit and threats --- a case even more complex and incredible than originally thought.