The First Omen movie is a prequel to the 1976 horror film, The Omen, and the sixth film in the franchise . The plot follows an American woman sent to work at a church in Rome, who uncovers a sinister conspiracy to bring about the birth of the Antichrist. Here is a detailed synopsis of the movie.

The movie follows Margaret Daino (Nell Tiger Free), a fresh-off-the-boat American novitiate in Rome, tasked to work at an orphanage prior to taking her vows.

She arrives at the Italian capital all wide-eyed and innocently excited, especially at a time when there is political unrest everywhere and people are turning their backs to the church.

Margaret immediately forms a bond with Carlita (Nicole Sorace), an unforgettable newcomer we’ll hopefully hear more from, delivering a performance both vulnerable and terrifying.

An eerie troublemaker like Margaret used to be during her problem-child days, Carlita gradually settles into Margaret's affection and protection, something that doesn’t sit well with the orphanage’s elders like the strict and intimidating Sister Silva (Sonia Braga).

The other elders in the film range from Bill Nighy’s high-ranking Cardinal Lawrence and Ralph Ineson’s Father Brennan, a character who looks like he just walked out of the set of the 1976 film and arrived at Stevenson’s prequel.

Also in the mazy mix is Father Gabriel, a young priest Margaret befriends before finding herself stuck deep inside a bone-chilling conspiracy where no one can be trusted.

The plot thickens as Margaret experiences demonic hallucinations, and she spots Paolo; horrified, he tells her to "look for the mark" before an oncoming truck fatally impales him.

Margaret sneaks into Sister Silva's office and uncovers a hidden, underground chamber and a series of subject files, all labeled "Scianna".

Each file contains a photo of a disfigured baby with a birthmark in the shape of three sixes, with Carlita as seemingly the only survivor.

She is intercepted and spots the mark on Carlita's palate before being imprisoned.

Father Gabriel frees Margaret; as they examine the files, they discover that another baby had survived. Margaret locates the mark on her own scalp and suddenly remembers that she was forcefully impregnated in a satanic ritual the night she blacked out at the disco.

The Devil will need to mate with his own spawn in order to conceive the Antichrist, and Margaret had been brought to Rome as Carlita is too young.

The group drives off to have the pregnancy aborted, but another car crashes into theirs on the way and Margaret's womb suddenly fills.

She awakens strapped to a hospital bed and is greeted by Cardinal Lawrence, the head of the conspiracy. She gives birth to two children, a girl and a boy; the latter is hailed as the Antichrist.

She stabs Lawrence but cannot bring herself to kill her son. Luz stabs Margaret as the conspirators flee with the boy and set the chamber ablaze to cover their tracks.

Carlita saves Margaret and her daughter and Margaret sees her assaulter, a demonic jackal in the flames.

The baby boy is given to American diplomat Robert Thorn to secretly replace the child his wife Katherine has supposedly miscarried.

Years later, Margaret lives secluded in the mountains with Carlita and her daughter, now a happy family.

Brennan appears and warns that the conspirators will be hunting her, and that her son has been named Damien.