In the early 1600s, a mysterious disease burns through the small French town of Bastion. Out of ideas, Father Martine Donadieu sends pleas for assistance. He receives an answer in the form of a pair of plague doctors.

When fledgling physician Pierre and his mentor arrive to brave the town's quarantine and get to work, they're surprised to find that while many are withering away to nothing, not a single person has actually died from this affliction.

In fact, they can't die.

Woefully unprepared to combat the rapidly spreading illness, the doctors and priest race to uncover the source of the town's sinister corruption. Left unchecked, all the citizens of Bastion will be at the mercy of the disease they have so aptly named the Withering.