It's 1887. High in the snow-swept Berkshires sits an old Romanesque convent where the nuns turn out bottles of their potent Italian amaro. They pray. They work. They pray some more. It's an isolated place where little gets in the way of the sisters' devotion.

Until now.

From a cavern lair far above the convent comes a predatory beast that stalks the good sisters: The Gulo.

The Hellish thing resembles both wolf and wolverine, with a massive maw of long, curved incisors and a thick hide covered in deadly quills. In a hideous pack, the creatures ravage some of the holy women and stalk off into the freezing forest hillside, but not before the nuns themselves manage to slay one of them.

Rather than risk the return of these fiends, the sisters decide to hunt them down. Fortified by their own powerful amaro-and by the bloodlust rising in them-they march into a raging gale of wind and snow with only makeshift weapons and a powerful medieval crucifix with a fire-hardened tip.

It's long odds for the brides of Christ.

But the appearance of a mysterious character turns the tide in their favor. The nuns can hardly believe it . . . but there she stands, a tall, striking woman who claims to have vanquished werewolves and other vicious bêtes in her native France. The strange warrior-saint gains the trust of the sisters who dub her the Long Nun. Though some think she hides a dreadful secret, too.

One thing's for sure, this Long Nun knows how to bring forth death. She trains the sisters in the ways of the hunt, encouraging them to heed their darker impulses, to abandon their churchly humility, and to seek violent vengeance against the Gulo. With their pagan and carnal senses heightened, the sisters take on the pack, becoming savages themselves, creatures bent on bloody revenge.

It's a true holy war, and a young postulant named Henrietta Q. documents all the grisly details in her battle book. But whether anyone will read it depends on the outcome of the fight-and on the mystery of the Long Nun.

Robert Eggers meets Emerald Fennell and Tarantino in the gothic horror thriller HAIL HOLY QUEENS