Father Martin Donadieu is out of time to turn back the plague that ravages the small French town of Bastion. Dispatching a frantic letter, he summons aid from the leading medical experts of the day: a pair of plague doctors.

Master physician Guillaume Jourdain and his young apprentice Pierre soon ride past the soldier-enforced quarantine and into town. The stakes of their mission made morbidly clear by the corpse of a man who tried to flee, now hanging in a tree near the entrance. There will be no retreat until their job is done.

It is not long before the doctors discover this is no ordinary ailment and that their medical training has left them woefully unprepared to combat the unnatural illness spreading around them. The disease saps the afflicted of all their strength leaving them no more than wheezing husks, yet no one has died.

With all the courage they can muster, Guillaume, Pierre, and Father Donadieu must race to discover the source of the town’s sinister corruption before the disease spreads to others, and themselves. Their dire mission will have them face the fetid, the unholy, and the eldritch. If they fail in their task, all will surely succumb to the disease they have so aptly named: The Withering.