In a flashback from 2001 in Louisiana, the Hastings family are preparing for what appears to be a serious conflict. Lighted torches outside their funeral home / residence are approaching, as they arm themselves with guns, weapons, and even some mystical objects. It won’t end well.
But we’re spared the carnage as a flash-forward takes us to present day, as Calvin, one of the Hastings boys, returns home from his Marine tour in Afghanistan. While a funeral is in session, Calvin is greeted lovingly by his mother Bea, and grudgingly by his father Isaac. While Calvin was away on duty, Bea rearranged the furniture in the house, and, in preparation for the upcoming Friday the 13th, armed the home with amulets and objects to ward off evil.
In conversation, we learn that Calvin is the only remaining Hastings son: his younger brother Arlo was killed under mysterious circumstances. Calvin has returned, on furlough, to help his family with “the fight” — probably similar to what happened 16 years ago. His father is not a little skeptical.
Later that night, at a Pentecostal revival, a religious ritual using snakes goes awry, and the snakes start to bite their handlers. The next day, a police team are performing forensics on the scene at which eight people died, and fifteen more were sent to the hospital. Could it have something to do with a mysterious white man named The Dredge (whom we’ll come to know is an infernal), and a gold coin with serpents on it he gave to a woman named Jessica? You betcha.
Later, Jessica is at home after the gruesome attack, when her roommate Nadine comes in to check up on her. A snake falls from Jessica’s bathrobe, and lurches at Nadine — before it kills her. So she becomes the LaRochelle police department’s number one suspect, and taken into custody. She’s also molting — or whatever it is snakes do with their excess skin. Isaac, who’s like the p.d.’s supernatural expert, is brought in to take a look.
It’s then that Isaac catches sight of the gold coin that The Dredge palmed off to Jessica. It’s got snakes embossed on it, and Isaac happens to know the special meaning it contains. Because he was there when it was first minted. Or something.
Tilly, the medical examiner at the funeral home, also knows a thing or two about world mythologies. The snake is the symbol for an ancient snake cult, that also dabbles in cannibalism. Whoever touches the coin takes on the appetite of a snake…and feasts.
Unfortunately, Officer Byron Wright also touched the coin, and is hungry for the flesh of his newborn baby. Calvin and Isaac show up at the Wright residence just in time, and the father-son duo kick Byron’s ass before he can do harm to either his wife or his child. However, Byron was able to shoot a little venom into Isaac’s eye before he was finished off.
Back at the funeral home, Isaac takes Calvin deep underground into the alchemy room where most of the good stuff happens. In it are all the tools necessary to perform exorcisms and other mystical rituals to countervail the force of evil. Isaac tells Calvin that because humans have so wrecked the planet, bad stuff is able to flourish. That means more work for their mom-and-pop shop.
And while Isaac finishes engraving bullets to make them infernal killing machines, he finally gets a chance to introduce himself to Garvey. She’s Isaac and Bea’s helper around the funeral home. She’s also his daughter. His and May’s daughter. He didn’t even know he had one… Well, apparently he went off to Afghanistan before the news broke.
But back to more important matters. Bea and Tilly did some digging, and there are 12 other of those snake coins out and about, and they need to find all of them to end whatever killing spree they’re causing. To do that, Bea has to participate in a ceremony that will let her divine their locations — but she has to touch the coin. The ceremony makes her sick, and she passes out.
More townspeople are touching the coins, going nuts, and killing. There’s some activity going down at the Garden of Eden Church — an apt location for some infernal festivities. Isaac and Calvin gear up for an incursion on the Garden of Eden Church. Meanwhile, the rest of the authorities have all been set on a wild-goose chase on the other side of town.
The infernal is somewhere in the church, as the readings on their electromagnetic devices indicate. When the father and son split up, Calvin is visited by the apparition of his dead brother…or rather, the infernal’s impersonation of him. Arlo begs Calvin to put a bullet in his head and free him from limbo. But what Calvin doesn’t know is that the bullet would pass through Arlo and go straight into Isaac. Luckily neither father nor son shoot at the other.
Then The Dredge finally appears, and hands over all the gold coins in exchange for what he calls a wonderful “piece of theater.” Must be Strindberg, given all the family dysfunction. The Dredge knocks out Calvin. Isaac tries his weapons on the infernal, but dispenses with all of them and goes right for fisticuffs. Calvin wakes up and, seizing a window, takes out a blade and decapitates The Dredge!
Oh, wait: it wasn’t The Dredge he decapitated. It was his daddy. Whoops. That's going to be a difficult one to explain to mom.