The campaign theme is one of treachery, with hidden powers of Chaos plotting the downfall of the Empire. The original material was published between 1986-1989 and was a big success with fans, being voted the Best RPG Campaign of all time by the French RPG Magazine Casus Belli.
The Enemy Within Campaign originally consisted of six books:
When the campaign was re-printed by Hogshead Publishing in the early 90s, they incorporated The Enemy Within text into Shadows over Bögenhafen. The Hogshead edition of Power Behind the Throne also includes an additional short adventure that was designed to make easier the transition between Death on the Reik and Power Behind the Throne.
James Wallis of Hogshead Publishing intended to re-design the final part of the campaign from the ground up. The final book would have been called Empire in Chaos. Sadly, this last book was never published (for more details on this, see the entry for Empire in Flames).