Inquisitor Gideon Ravenor and his retinue are believed dead and, with shadowy forces moving against them, they'd like to keep it that way. Returning back to the planet Eustis Majoris, they go undercover, investigating a brutal ring of smugglers moving stolen arcane technology within the Imperium. As they descend deeper into the organisation, it becomes clear that a terrible plot is unravelling. The ancient machines contain the unthinkable, and Ravenor must summon all of his wits to thwart the conspirators before the ultimate secrets of Chaos itself are laid bare.