From the publisher's website:
"Our enemies prowl in the shadows of shining cathedrals. They scuttle in the darkness of dank underhives. They lurk in the corners of gilded palaces. They even dare to stand openly, hiding behind false faces and honeyed words. They are everywhere that man live and breathe – and so we must always be ready to face them with fire and the Emperor’s wrath!”
–from the Epistles of Inquisitor Kharkov
Cults fester throughout the Askellon sector. Only the valour and vigilance of the Ordo Hereticus prevent the Imperium from tearing itself apart in a blood-soaked spasm of fear and madness. These men and women of the Inquisition stride through worlds rotting beneath the heresy of cultists, mutants, and witches. It falls to these fearless Acolytes to bank the coals and stoke the flames, bringing the purifying fire of the Emperor to every corner of the galaxy. To save the lives of billions, millions more must burn.
Enemies Within is a supplement for Dark Heresy Second Edition, bringing new backgrounds, talents, and roles for you to join the Ordo Hereticus in their thankless quest. You may rise from the Adepta Sororitas to take the Sister of Battle elite advance, or you may take up new weapons and items specially suited to rooting out heretics of all kinds. New planet types offer grounds for your inquests, while a host of unnatural cults offer the seeds for countless campaigns. With the cult and plot generator in this supplement, the possible adventures are truly limitless. Prepare to face the enemy within!