WARNING: The following contains spoilers for The Third Day, now airing on HBO.
With Jude Law's Sam stuck on Osea Island in The Third Day, it's clear that some malevolent force is keeping him there. Multiple conveniences pop up that leave him stranded, whether it's the causeway flooding, a truck blocking his vehicle, Jess luring him in to continue their affair or him being a good dad and wondering if young Epona will be abused by her sick father when he leaves.
However, as Sam explores the island, whether in a dream or physically, he sees a mysterious kid -- a curly-haired ghost that appears to be tethered to the place and possibly the avatar of what's got a hold on him. Now, in the second episode, viewers get further insight into the history of Osea, and it paints an ominous picture of death that could be connected to the boy.
In "Saturday -- The Son," Jess reveals that there are religious ties to Osea, which Sam suspects after seeing animal sacrifices around and pictures of a Jesus-like figure being hung upside down. Jess pulls from some real-world history, admitting the secluded island was purchased by Frederick Nicholas Charrington and turned into a retreat for alcoholics in the early 1900s.
The brewery scion felt this would be therapeutic, but it also allowed pagans to reside, with current occupants adhering to their ancient traditions. Their beliefs are connected to Christianity, while the major practices are tied to Celtic gods. That Jesus-like figure is actually Esus, a Celtic war god, whose victims were sacrificed by being ritually stabbed and hung from trees, which stuns Sam. Jess isn't disturbed, though, as she's visited a few times and her academic background leaves her with an open mind.
It turns out the Celts think Osea is the "soul of the world," and during the "Esus and the Sea" festival, locals known as the Sajora run around with fish-shaped burlaps sacks over their head. They use giant scissors in their hands, pretending to cut out the evil in children, and while it's disconcerting, the natives now want to make all this more digestible for tourists. They've taken massive revenue hits with their oyster industry crumbling, so the festival is now being turned into a musical festival for mainstream visitors, although Jess notes that the scary aspects of the island are being kept to a minimum.
This leaves Sam wondering, however, if visions he's been having where he's cutting himself open, possibly ripping his heart out, could be tied to this religion. It's a nightmare that feels all too real, and when Sam hears the other details, he starts to panic. It turns out the weekend festivities are linked to a trinity of gods, not just Esus. Along with Toutatis and Taranis, they make up the Threefold Death in Celtic lore with a hero dying as a sacrifice via three ways -- Toutatis is fire, Taranis is drowning and Esus is hanging.
Things get even more eerie as he takes note of Jess confessing how tourists don't want to know they're "glamping on the site of sustained ethnic genocide," as Celt extremists in the past were said to have sacrificed people as part of the island's religion. It's not something they want to be advertised, and Sam immediately recalls a church session with Epona's dad about sinning, rebirth, redemption and salvation, which has him thinking he's surrounded by a cult. At this point, while Sam's in denial, to the viewers it appears that Sam's purpose on Osea is to ensure the land is bountiful again by being a sacrifice.
Later on, Epona warns him that a darkness is coming and Sam wonders if it's from that revival tent and the fervent worshippers, obsessed with their war gods. It's why they seem to have pictures of victims of Jack the Ripper in the main pub, hinting they were also occult sacrifices. From what Jess says, things haven't evolved much, and while she downplays things, Sam is smack dab on an island where convicts came to work and died, where soldiers such as his grandfather were stationed during World War I and where people have been offered to deities. At this point, Osea isn't a battleground, it's a death bed, and whether it's the ghost or Jess, Sam's been baited. It all comes to a head when Epona's dad knocks him out as he roams around high off an LSD session with Jess as the episode ends, foreshadowing that he's about to meet his maker.
Starring Jude Law, Naomie Harris, Katherine Waterston, Nico Parker, Charlotte Gairdner-Mihell, Paddy Considine and Emily Watson, The Third Day airs at 9 p.m. ET/PT on HBO.