The plot revolves around the crisis of faith suffered by Father Lankester Merrin following the horrific events he witnessed during World War II. Many years before the events in The Exorcist, the young Father Merrin (played by Skarsgård, who played the same part in Dominion: Prequel to the Exorcist) travels to East Africa. Merrin has taken a sabbatical from the Church and devoted himself to history and archaeology as he struggles with his shattered faith. He is haunted especially by an incident in a small village in occupied Holland during World War II, where he served as parish priest: near the end of the war, a sadistic Nazi SS commander, in retaliation for the murder of a German trooper, forces Merrin to participate in arbitrary executions in order to save a full village from slaughter.After World War II, Merrin is an archaeologist in Cairo, when he is approached by a collector of antiquities who asks him to come to a British excavation in the Turkana region of Kenya. This dig is excavating a Christian Byzantine church built circa 500 A.D. long before Christianity had reached that region of Africa. The collector asks Merrin to recover an ancient relic of a demon before the British can find it. Merrin agrees and travels to the dig site. He is joined by Father Francis, a Vatican scholar who was on his way to do missionary work in East Africa but was diverted by the Vatican to ensure the church is not desecrated. Upon arriving at the site, Merrin meets Major Granville, the British military officer in charge of the dig. Merrin also meets the chief excavator, a brutish man with visible boils on his face. And he meets Sarah, a doctor who spent time in a concentration camp during World War II and is haunted by what happened to her there. Merrin's translator and guide is Chuma. In addition, Merrin learns that the diggers are disappearing or leaving in droves because the local tribemen fear the church is cursed. Merrin witnesses a digger inexplicably experience a seizure.Merrin visits the dig site. Only the dome is uncovered; the rest of the church is buried beneath the earth. Merrin discovers that the church is in perfect condition, as though it had been buried immediately after its construction were completed. Merrin, Francis, and Chuma enter the church through the dome. They find it is near-pristine condition, but there are two oddities. First, all of the statues of the angels holding weapons are pointing the spears downward, whereas it is conventional for statues of angels to either have no weapons or to point them triumphantly toward heaven. Merrin and Francis deduce the sculptors were trying to depict the angels restraining something that was beneath the church. The second disturbing discovery is that someone has vandalized the church by ripping the enormous crucifix from its place on the altar and suspending it with Christ on the cross in an upside-down position, which is considered a desecration.Merrin is determined to learn more about the archeological dig and asks to consult with the lead archeologist, Monsieur Bession. Sarah tells Merrin that Bession went insane three weeks earlier and was transferred to a mental hospital in Nairobi. Merrin visits Bession's tent at the dig site and sees dozens of drawings of the same thing, the demon artifact the collector had asked Merrin to find. Merrin then travels to Nairobi to visit Bession. But when he enters Bession's room, he discovers Bession has carved a swastika on his chest and is speaking through demonic possession in the voice of the sadistic SS commander who tormented Merrin during the war. As Merrin registers these events, Bession slashes his own throat after saying he was "free." Father Gionetti, warden of the asylum, speculates that Bession was not possessed but rather "touched" by a demon, which drove him mad and eventually to suicide. Merrin is very skeptical, but before he returns to the dig site, Father Gionetti gives him the volume of Roman rituals to use in exorcism, although Merrin claims he will never use them.Upon returning to the village, strange events continue. A local boy is attacked and killed by hyenas that seem to continuously stalk the dig, night and day. His younger brother, Joseph, enters a fugue state after watching his brother ripped to pieces. Merrin begins to suspect that something evil lies in the church and is infecting the region. There are stories of an epidemic that wiped out an entire village. However, when Merrin, growing suspicious of these rumors, digs up one of the graves of the supposed victims of this plague, he discovers it is empty. Meanwhile, the evil grows, turning people against each other and resulting in violence, atrocities, and more bloodshed.Father Francis reveals to Merrin that the builders of the church never meant it to be recorded in Vatican documents, however, a vague reference to it was recorded, leading to its subsequent discoveries in the 19th and 20th centuries. Francis also reveals that the church stands on the supposed site where Satan fell to earth after the war in heaven, and it was constructed by early Christians in an attempt to purify the evil that resides there.Beneath the church lies the ruins of an even older temple but not a Christian one. Rather, in the ruins under the church, Merrin and his allies find demonic icons, and other signs of evil and Satanism. This land is where he first encounters the demon that calls itself Pazuzu, which he will encounter again in The Exorcist. This is the demon that "brushed" Bession (driving him insane) and Joseph (making him ill).At the end of the movie, the dig's doctor, Sarah, turns out to be the possessed individual and has the demon exorcised from her in the tunnels below the church but dies. Dr. Merrin and Joseph emerge from the church, (once again buried in sand) and history has repeated itself. 50 (and 1500) years ago, everyone at the site was killed by an evil presence from the church, except for one priest. Now, only Father Merrin and the little boy are left as the British soldiers and the local tribes have annihilated each other. Merrin returns to Rome and meets with the collector at a cafe, explaining he was unable to find the relic, the collector replies, "But you found something....Didn't you?"... As he leaves, Merrin is revealed to be wearing a collar and is now a priest again, having regained his faith in God, after defeating the demon with holy exorcism rituals.
What did the collector ask Father Lankester Merrin to recover?
An ancient relic of a demon