Under the Sun of Satan

Donissan, newly ordained as a priest, deeply doubts his vocation and feels unworthy of his calling. He subjects himself to ritual flagellation as a way to prove his worth and seek spiritual certainty, believing that physical suffering might compensate for what he perceives as his spiritual inadequacy. His mentor Menou-Segrais recognizes this as a troubling sign but also sees potential for good in the young priest if channeled through faith rather than fear.

Mouchette, a 16-year-old brewer's daughter, visits her lover the Marquis de Cadignan to ask for help fleeing to Paris. When Cadignan admits he cannot assist her due to financial troubles, she stays the night. The next morning, while playing with his loaded shotgun, the weapon discharges and kills him. The death is ruled a suicide, though Mouchette knows she is responsible. Her desperation to escape her circumstances and the fatal mishap with the loaded weapon lead to the tragedy.

After Donissan encounters Mouchette wandering in the fields, he uses his newly discovered ability to perceive her innermost thoughts and reveals that he knows she killed Cadignan. He urges her to repent for her sin. Overwhelmed by guilt and unable to bear the weight of her secret being exposed, Mouchette returns home and cuts her throat with a razor. Donissan's confrontation with her conscience proves devastating rather than redemptive.

After discovering Mouchette's body, Donissan carries her bleeding corpse to the church and lays it before the altar in a radical act of intercession. He hopes that by presenting her body in a sacred space and praying over it, he might save her soul despite her suicide, a grave sin in Catholic teaching. This audacious act shocks the community but simultaneously begins establishing his reputation as a holy man willing to defy convention for the sake of souls.

Earlier, Menou-Segrais noted that Donissan had extraordinary potential to do good if guided by faith.

During the encounter in the fields, the mysterious horse-trader, who is actually Satan, reveals that Donissan has the rare and troubling ability to look directly into the souls of other people. This supernatural gift allows him to perceive others' innermost thoughts and lives, which Satan describes as both powerful and dangerous. This ability first manifests when Donissan confronts Mouchette, seeing her entire life and her sin of killing Cadignan.

A farmer begs Donissan to pray over his dying young son. Donissan approaches reluctantly, feeling unworthy, but enters the boy's bedroom and lifts the body in prayer. According to the witnesses present, the child's eyes then open, a moment interpreted as a miraculous resurrection. While the film presents this as a genuine miracle, it also emphasizes Donissan's internal turmoil and unworthiness, leaving the event suspended between divine intervention and the power of desperate faith.

After the strain of his spiritual duties and growing reputation for miracles, Donissan suffers a nocturnal assault by Satan, presumably a spiritual rather than physical attack. During this torment, he prays to God to spare him if there is still purpose for his suffering. He survives the night and resumes his duties, though the attack leaves him further weakened and more deeply entangled in his struggle between divine purpose and demonic pressure.

After recovering from Satan's attack and returning to his duties, Donissan continues hearing confessions until the very end. When Menou-Segrais visits the confessional after the last penitent leaves, he discovers Donissan dead. The film presents his death as the culmination of a life defined by relentless spiritual trials, self-flagellation, encounters with evil, and the burden of his supernatural gift. He has borne the trials of his faith to the very end, dying in the sacred space where he served others.

Earlier, Donissan prayed to God to spare him if there was still use for his suffering.

When Donissan confesses his doubts and unworthiness, Menou-Segrais tells him it is not too late to choose another path, but also recognizes in him a substantial capacity for good that could become a powerful force if guided properly by faith. This observation proves prophetic, Donissan goes on to perform seemingly miraculous acts and becomes venerated as a holy man. Yet his path to doing good is tortuous, marked by self-destruction and tragedy, suggesting the potential Menou-Segrais sees is real but comes at enormous personal cost.

Donissan later brings Mouchette's body to the church in an act of radical compassion, and performs a miracle over the dying boy.