Daniel has a spiritual awakening while serving his sentence in a youth detention center for second-degree murder, but his criminal background prevents him from pursuing his dream to become a priest once he is released. He is assigned to work in a sawmill in a small town, and while visiting the local church, he pretends to be a priest. The vicar of that church meets Daniel wholly believing his lie, and leaves him in charge of the church while he goes to rehab for an alcohol problem. Daniel begins performing all the duties of priesthood, and enjoys it. The parishioners enjoy his unorthodox methods, even his unexpected claim from the pulpit to be a murderer, but they have mixed feelings when he starts asking about a recent car accident that caused a lot of trauma in the community. The more time he spends there, he begins to uncover the small town's deep secrets: it's still unclear whether the car crash was actually an accident, but the mayor insists that the issue has been put to bed. The biggest point of contention is whether the driver should be allowed to be buried in the town's cemetery with the other victims. Daniel discovers that after months, the cremated remains still haven't been buried anywhere, and many in the town had sent hateful, threatening letters to the widow. He and his new friend Marta confront the townspeople about this, showing them the letters with their handwriting, and Daniel decides to go forward with a funeral at the cemetery. Marta is thrown out of the house by her mother for bringing out the letters, and she asks to stay at the temporary rectory with Daniel; while there, they make love. During the funeral, many of the townspeople put aside their hate and pay their respects, and at the end of the ceremony, the priest from Daniel's youth detention center arrives, having been tipped off that the town's new priest is an impostor. He tells Daniel to pack his bags immediately, but Daniel sneaks out a window and goes to the church to celebrate his "farewell Mass". During the Mass, he removes his vestment and shirt, showing all his tattoos, and leaves the church. Daniel is sent back to jail where he again has to face the brother of the man he murdered. At the detention center Daniel fights the brother of the boy he murdered and after gaining the upperhand in the fight he is allowed to walk free by other inmates.
The script for Corpus Christi was written by Mateusz Pacewicz with consultation help from Krzysztof Rak, but after director Jan Komasa read it, he felt the story and especially the character of Daniel needed to be pushed further, so he added a "troubled background" to Daniel's story. Komasa has also said that the car accident that caused such trauma for characters in the film is a symbol for the 2010 Smolensk air disaster, in which 96 people died in a plane crash, including Poland's president and top officials. The film's cinematography was shot in a "a grim, desaturated palette". The film's production ran into controversy because a man claimed the film was actually based on his real life experiences and his efforts to get in contact with the film's producers were met with silence. The producers have said that the film is not based on this man's life, and instead on various cases of fraud in the priesthood. Pacewicz has said that fake priests are a fairly common occurrence in Poland, and every couple months a new case is discovered; they are often "about the need for a sort of social security for the underprivileged to become a trustworthy priest which is a great form of social status for many".
The review aggregator website Rotten Tomatoes reports an approval rating of 98% with an average score of 7.84/10, based on 63 reviews. Variety's Peter Debruge called the film "stunning" and "quietly subversive", despite a few plot points that feel like a soap-opera to him. "Bielenia is never less than totally compelling," wrote Christy Lemire for RogerEbert.com, adding that "this is a complex character full of layers and contradictions." Writing in the Polish magazine Polityka, Janusz Wróblewski described the film as more suspenseful than the classic Western films, and lauded the ways in which it exorcises the complexities of Poland's past.
