Reliquary

Claire Sutherland, a freelance social media manager living in Connecticut, receives a call informing her that her fiancé, Elias Ashbury, a wealthy hedge fund manager, has died of a brain aneurysm. At the hospital, the neurologist shows her CAT scans revealing years-old lesions so severe that Elias should have been incapacitated long ago. Claire notices the fatal aneurysm looks strangely like tentacles. On the drive home, a car with bright blue LED headlights follows her, echoing a period in college when she believed a similar vehicle was stalking her. At the house, she discovers Elias added her name to the house deed, car titles, and bank accounts before his death. The octopus-like creature he kept in a massive aquarium has also died.

Claire dreams of Elias hovering with yellow, oversized eyes and a masklike face. He tells her cryptically that what is coming will be a lot and that she is the right person for it. A letter arrives from Audrey Ashbury, Elias's mother, inviting Claire to the family home at Harrow Point, a private island off the coast of Maine, to celebrate Elias's life. The visit begins on May 4, Claire's birthday. She accepts, eager for connection to the family she never met during her five-year relationship with Elias.

A flashback reveals how Claire and Elias met at Coney Island, where a fortune-telling machine produced the card: "You will always go back to the ocean." Elias had recently finished five years of unspecified work for his family's company, Ashbury Marinography. He offered Claire stability, something she had lacked since a childhood boating accident killed her family. Two years into their relationship, Claire was struck by a black car with blue headlights in a hit-and-run. Elias proposed shortly after, though he repeatedly refused to set a wedding date, always saying he loved her too much.

Claire flies to Portland on the Ashbury private jet. Audrey greets her warmly, calling Claire "my daughter" in French. They cross a causeway to Harrow Point, where the house is a sprawling gothic structure built into a cliff, its lower windows submerged beneath the waterline. Inside, a grand staircase leads downward rather than up. Claire meets the patriarch, Wellington Ashbury V; his brothers Patrick and Greg; Greg's husband, Theo; and Patrick's wife, Dierdre. All possess strikingly blue eyes. Elias's older half brother, Wellington VI, known as Ash, appears from the shadows, immediately antagonistic about the family's "initiation" of Claire.

The Ashburys throw Claire a birthday party with cake that tastes oddly sweet and sour and gift her a high-end film camera. At dinner, she learns Elias's biological mother was Josephine, Audrey's older sister, who died; Audrey married Wellington afterward. Wellington shows Claire the Poseidon, a glass submarine housed deep beneath the ocean where every Ashbury wedding night takes place. That night, Claire realizes Ash's raspy voice matches a voicemail left on her landline before Elias died. Ash confirms he called and begins to warn her, but is interrupted. Theo gently advises Claire not to put the Ashburys on a pedestal.

At three in the morning, Claire observes Wellington, Patrick, and Greg kneeling before the underwater windows, worshipping something vast in the dark water. She stumbles into an unlocked room plastered with tabloid clippings: a front page featuring her seventh-grade photo beneath a headline about her miraculous rescue from a shipwreck, alongside faded clippings showing younger versions of Theo and Dierdre. The next day, Wellington performs a ritual on a yacht, dedicating a sacrifice called "Mike" to the sea. Theo privately urges Claire to leave. That night, she sees a staff member eating from a tub and spots a human finger: Mike was a person.

Ash pulls Claire aside. As they climb a back staircase away from the water, where the god can listen, he reveals everything. The Ashburys worship a sea god, a tentacled Leviathan that periodically requires a human body to inhabit. Claire's visit follows a four-day ritual called the Four Stations: Arrival, Anticipation, Acceptance, and Ascension. The god chose Claire and sent Elias to lure her into the family. Ash was originally supposed to deliver her but refused and fled. Elias took over but stalled for years, delaying the wedding, and the god killed him by triggering the brain aneurysm. The house staff are failed vessels called "skins," bodies that decayed into monstrous forms because they lacked the significance of a true sacrifice. The birthday cake was laced with sedatives to keep Claire compliant.

They attempt to escape by car, but the god, inhabiting Elias's decomposing corpse, manifests in the back seat and tears into Claire's side with tentacles. The car crashes off the causeway into the sea. Claire wakes bound to an altar in an underwater cathedral, wearing a white wedding dress. Patrick officiates a forced marriage between Claire and Ash. The skins file past in a ritual called the Witnessing. Lucille, a staff member who is also Audrey and Josephine's younger sister, plunges her hand into Claire's wound and tears out a piece of intestine. The god, still wearing Elias's body, heals Claire and declares her its "Eternal Skin": the permanent human vessel it intends to inhabit.

Sedated and placed aboard the Poseidon, Claire and Ash smash hidden cameras and exchange confessions. Ash admits he was Claire's college stalker, watching her from a black BMW, and that he deliberately hit her with the car to delay the Ashburys' plans. Claire confesses that the boating accident that killed her family was partly her fault: She accidentally disabled the radio. Trapped in a tackle chest as the boat sank, she promised a voice in the waves anything in exchange for survival. The voice accepted, calling her its "eternity." Ash confirms this bargain is why the god will never stop pursuing her.

The Ashburys march Claire to the clifftop for the Ascension, the ritual's fourth and final stage. Wellington invokes the Leviathan. The god arrives in its true form: a mass of tentacles vast enough to obscure the sky. It swallows Claire. Inside its throat, a projection of Elias coaxes her to surrender. Claire nearly gives in, then realizes she has never tried to fight. She wrenches free of the digestive fluid bonding her to the creature, tears a flap of dead flesh from her arm, and shoves it at the god, declaring that piece is all it will get. Unable to force an unwilling sacrifice, the god convulses and vomits her out.

On the cliff, Wellington tries to force Claire back into the god's mouth. Ash breaks free from his guards and slams into Claire, knocking her away from his father. Ash runs into the god's mouth and merges with it, becoming a towering figure with his face, glowing blue eyes, and tentacles. He releases the penned skins, who devour Patrick and Greg. Claire shoves Audrey off the cliff. Wellington stumbles over the edge. Theo drives Claire and Dierdre to a yacht, and they sail from Harrow Point. In the bathroom mirror, Claire discovers her left eye has turned electric blue. She feels an unfamiliar hunger.

Over a year later, Claire lives in a small Maine coastal town, working at a crab shack and building genuine friendships. She has one brown eye and one blue, craves rare meat, and her scarred arm itches constantly. When a news report reveals that an employee of Rhodes-Hodge Infrastructure, an Ashbury-linked sister company, has vanished during a retreat, echoing the pattern of corporate-sponsored sacrifice, Claire boards the Poseidon, which Dierdre delivered to her months earlier. She dips her scarred fingers into the ocean, and bioluminescence sparks around her hand. Ash appears inside, looking mostly human but changed, with scaled skin and glowing eyes. Claire tells him she intends to fulfill her childhood promise her own way: not as a passive sacrifice, but by using the hunger and power the god left in her. She proposes they start with Rhodes-Hodge. Both smile with sharp teeth, and the Poseidon descends into the sea.