When God (Frances McDormand) created the Heaven and the Earth on Sunday, October 21, in 4004 BC at 9:13 a.m., she initiated a joke that paleontologists haven’t noticed yet (dinosaurs and evolution aren’t real) and a game that she plays by her own rules. And since the first humans walked the Earth, and Adam (Anthony Kaye) and Eve (Schelaine Bennett) were thrown out of the Garden of Eden, angel Aziraphale (Michael Sheen) and demon Crowley (David Tennant) have been here.
The serpent that tempted Eve? Crowley. The angel that gave Adam a flaming sword for protection outside the Garden? Aziraphale. As they watched the two leave Eden to experience the harsh desert and thunderstorms beyond its walls, the two formed an unlikely bond. They may be supernatural adversaries, but from the beginning they both rather like Earth.
Fast forward to 11 years ago, when Arthur (Daniel Mays) and Deirdre Young (Sian Brooke) arrive at their local convent hospital to deliver a son at the same time Harriet Dowling (Jill Winternitz), wife of American Ambassador Thaddeus Dowling (Nick Offerman), arrives to deliver hers. Unbeknownst to any of the expectant parents, they’re in the hands of Satanic Nuns of the Chattering Order of St. Beryl– nuns who have been tasked with swapping out the Prince of Darkness for the Ambassador’s child.
In a cemetery near the hospital, Crowley meets fellow demons Duke of Hell Hastur (Ned Dennehy) and Duke of Hell Ligur (Ariyon Bakare). They trade recent successes (in terms of turning souls towards hell), and then the Dukes present Crowley with a picnic basket containing the Son of Satan.
Crowley, blasting Queen, reluctantly takes the baby to the convent. Planting the baby with human parents is the first step towards the Apocalypse, and although that’s something Crowley is comfortable with in theory, he doesn’t actually want the world to end.
When he arrives, his disinterest in his task, combined with the confusion created by the extra set of delivering parents, leads to a little mix up. Instead of subbing the Prince of Darkness for the Ambassador’s baby, Crowley and an unwitting nun accidentally give him to the other couple. The child of the Youngs is given in error to the Dowlings, and the Dowlings’ actual child is… taken elsewhere. (Probably to a very happy life, according to an insincere voiceover from God.)
Believing that he’s set the wheels of Armageddon in motion, Crowley rings up his old friend Aziraphale. Aziraphale has already been tipped off to the fact that the end times are afoot by the angel Gabriel (Jon Hamm), but Gabriel doesn’t know that Aziraphale would be sorry to see Earth go– even if Heaven were to win the ultimate war for souls. Aziraphale likes eating and classical music and old books. And he likes Crowley, whom Gabriel doesn’t know he’s ever met.
Crowley leans on Aziraphale to work with him to prevent the end of the world they both enjoy so much, and ultimately they agree that if Crowley is fulfilling his orders of influencing the boy towards evil as he grows, and Aziraphale shows up to thwart Crowley by influencing the boy for good, they’re both technically doing what they’ve been asked to.
They take jobs with the Dowling family, Crowley as young Warlock Dowling’s (Rocco Day) nanny, and Aziraphale as the family gardener. As the boy moves towards his 11th birthday, when he will receive a Hell Hound and come into his full power, they manage to negate each other’s efforts well enough that the boy seems harmlessly normal. If they can prevent him from naming the Hound when it arrives, they feel fairly certain they’ll have prevented Armageddon.
When the fateful day arrives, the Hell Hound doesn’t. Somehow, in 11 years, this is their first clue that they’ve got the wrong boy.
The Hell Hound finds the real Son of Satan, Adam Young (Sam Taylor Buck), playing happily in the woods near his home with his best friends, “The Them”: Brian (Ilan Galkoff), Pepper (Amma Ris) and Wensleydale (Alfie Taylor). It snarls unseen, listening while Adam tells his friends that what he really wants for his birthday is a clever little dog he can have fun with– one that can go down rabbit holes and that he can teach tricks. Then it hears Adam give it a name– the thing that will give the Hell Hound its purpose, its function, its identity: “Dog.”
Dog transforms into a terrier, bounds into the idyllic scene and claims his master, Adam “Son of Satan” Young.