Set during World War II, The Faust Conspiracy centres on a plot by the Germans to kill 'Faust', the codename for a high ranking British target, by sending in Karl Vogel, a trained assassin. The operation is partly to forestall the activities of the Anti-Hitler Conspiracy, a group of German military officers who want to kill Hitler, replace him and the Nazis with a more moderate leadership and negotiate a peace with the UK and the USA. This group find out about Vogel's mission, but not who the target is, and decide to send two of their own agents, Keller and Lorenz, into the UK to try and prevent the assassination, realising just how much harm would be done to their own plans if it were to succeed. Unfortunately, it is Keller's group that attracts the attention of MI5, triggering a massive manhunt. Keller has to prevent Vogel from carrying out his mission while trying to evade capture by MI5 - and 'Faust' turns out to be even more important than anyone thought...