In 1348 in a plague-ridden medieval England, novice monk Osmund has a secret relationship with a young woman named Averill who has taken sanctuary in his monastery. When the disease strikes the monastery, Averill departs at Osmund's urging, but promises to wait one week for Osmund at a nearby forest. Osmund prays for a sign from God to leave the monastery and reunite with Averill. Shortly afterwards, Ulric, an envoy for the regional bishop, arrives at the monastery seeking a guide through the forest to reach a remote marshland village untouched by the plague. Taking Ulric's arrival as the sign to leave, Osmund volunteers to serve as the guide and joins his group, which consists of soldiers Wolfstan, Griff, Dalywag, Mold, Ivo, and Swire. The group informs Osmund that the village is believed to be led by a necromancer, who they intend to deliver to the bishop for trial and execution.
The journey to the village leads to the deaths of Griff and Ivo, while Osmund finds Averill's blood-stained clothing and believes she has died. Eventually reaching their destination, the group are met by Hob and Langiva, the village's leaders. Aware of the group's intentions, the villagers drug the soldiers, while Osmund learns that Averill's body is in the village and witnesses Langiva perform a ritual that revives her.
The members of the group are bound and placed in a water-filled pit where Hob and Langiva offer freedom to those who will renounce God. When the group refuses, Dalywag is crucified and disemboweled. The sight causes Swire to renounce his faith, only for the villagers to hang him in the woods. Afterwards, Osmund is brought to Averill and believing her to be in a state of suffering, stabs her to save her soul. Ulric is then taken from the pit to be dismembered by horses, but before the villagers execute him, he reveals that he is afflicted by the plague and has brought it to the village. With the villagers distracted by this revelation, Wolfstan and Mold are able to free themselves with a knife Osmund snuck by the pit and fight back. Hob kills Mold, but is incapacitated by Wolfstan and placed in the device for transporting the necromancer.
Osmund pursues Langiva to the swamp, where she tells him that she is not a witch and Averill did not die in the forest. Instead, Averill had been drugged and her apparent resurrection was an act; her actual death was caused by Osmund stabbing her. Broken by this information, Osmund is unable to prevent Langiva from escaping. Wolfstan, deeming the mission to be completed, returns Osmund to the monastery, with Hob to be delivered to the bishop. In the following years, the village becomes afflicted by the plague while Wolfstan loses contact with Osmund, but hears rumours of him becoming cold and cruel as he dedicates himself to finding and punishing Langiva.
Eddie Redmayne as Osmund
Sean Bean as Ulric[6]
Carice van Houten as Langiva
John Lynch as Wolfstan
Tim McInnerny as Hob
Kimberley Nixon as Averill
Andy Nyman as Dalywag
David Warner as The Abbot
Johnny Harris as Mold
Emun Elliott as Swire
Tygo Gernandt as Ivo
Jamie Ballard as Griff
Daniel Steiner as Monk
Nike Martens as Elena