Silver Nitrate

Set in Mexico City in 1993, the story follows Montserrat Curiel, a freelance sound editor, and her lifelong best friend Tristán Abascal, a former soap opera star. Montserrat is the only woman on the editing team at Antares, a post-production studio, where she is perpetually passed over for full-time work. Tristán's acting career collapsed a decade earlier after a car accident killed his girlfriend, Karina Junco, leaving him with a reconstructed face and a tabloid reputation as a reckless party animal, compounded by coded gossip about his bisexuality. He now earns a modest living doing voice-over work. Montserrat has loved Tristán since childhood, though their bond is uneven: when he is in a relationship, he forgets her; when single, he clings to her.

After a breakup, Tristán moves to a new apartment in the Granada neighborhood and discovers that his neighbor is Abel Urueta, a once-celebrated Mexican horror film director from the 1950s. Charmed by Abel's stories of Golden Age cinema, Tristán brings Montserrat to dinner. Abel reveals the history of his unfinished fourth film, Beyond the Yellow Door (1961), and its co-writer: Wilhelm Friedrich Ewers, a German occultist who believed cinema could channel real magic.

Ewers developed a syncretic magic system combining European runic traditions with knowledge stolen from Indigenous practitioners across South America and Mexico. He believed silver nitrate film stock was a powerful magical conduit and that post-synchronized sound, where image and audio are recorded separately then merged, functioned like closing a circuit for spells. His system required three performers on screen: a "father" (Ewers), a "son" (Abel), and a "mother." The film was financed by Alma Montero, a wealthy former silent film star who believed the spell would restore her youth. Ewers secretly replaced Alma with Abel's fiancée, Clarimonde Bauer, and redirected the spell to save his own failing heart. When Alma discovered the betrayal, she shut down production. Ewers was subsequently killed. Abel claims everyone connected to the film suffered terrible luck due to the incomplete spell.

Abel has secretly kept one reel and the undubbed third scene's script. He asks Montserrat and Tristán to help finish the dubbing, hoping to break the curse. At midnight in the Antares studio, they record their voices: Abel reprises his role, Tristán speaks Ewers's lines, and Montserrat provides Clarimonde's part. A string of good fortune follows. Tristán lands a major soap opera role, Abel is offered a career retrospective, and Montserrat's sister Araceli, who has been undergoing cancer treatment, sees her tumor nearly vanish.

Disturbing side effects soon emerge. Tristán begins seeing Karina's ghost in his apartment, bloodied and dripping glass. Abel's drinking intensifies and he phones Montserrat obsessively. Montserrat studies Ewers's book, The House of Infinite Wisdom, and discovers a hidden autobiographical letter sewn into the binding. It reveals Ewers's plan for self-resurrection: after his film was completed and screened, he intended to commit ritual suicide and be reborn in a healthy body.

Abel calls Montserrat in a panic, saying Alma has demanded the return of all Ewers's artifacts and threatened consequences. That night, he calls again in terror and the line goes dead. Montserrat drives to his apartment and finds his body with his throat cut. After being detained and released by police, she resolves to track down Alma, Clarimonde, and José López, a magic practitioner connected to the original production. She and Tristán break into Abel's apartment and discover the dubbed film duplicate has been stolen.

Through Tristán's contacts, they meet Alma's supposed niece, Marisa Montero, who claims Alma is living in Acapulco and reveals that López and the film's credited screenwriter, Romeo Donderis, are the same person. Montserrat traces Clarimonde to her home in the wealthy Las Lomas neighborhood. Clarimonde confirms she has the duplicate and reveals Abel's murder was Alma's doing. She insists the only way to end the curse is to bring Ewers back from the dead and demands the original nitrate print. When Montserrat refuses, Clarimonde tries to cast a hex by drawing runes, but Montserrat counters it using a symbol from a secret alphabet she and Tristán invented as children. The paper Clarimonde was drawing on bursts into flames.

After Tristán's apartment is ransacked, José López rescues them from conjured beasts and brings them to his warded home. López reveals the full truth: he and Alma murdered Ewers in 1961 after discovering Ewers planned a human sacrifice. Rather than destroying the magic, the murder inadvertently completed the blood sacrifice the spell required. Alma used the residual power to halt her own aging for decades; the woman calling herself Marisa is actually Alma herself. By dubbing the film, Montserrat and Tristán triggered a second surge of magical energy, granting Tristán necromantic abilities and Montserrat fire and defensive magic, while also accelerating Ewers toward physical manifestation.

López proposes a plan: draw six specific runes in the correct sequence using blood on the nitrate film can, then destroy the film to symbolically end Ewers's existence. Only Abel knew the correct order, so Tristán must summon his ghost. After privately confessing his guilt over Karina's death and bidding her ghost farewell, Tristán contacts Abel through automatic writing in a séance. Abel provides the rune sequence, but Ewers invades the session and attacks violently, injuring López, before Montserrat and Tristán drive the entity back.

They rush to Antares to retrieve the nitrate print and encounter Alma in the hallway, now visibly aged as her stolen youth drains away. She attacks with electricity-based magic. Montserrat spots Ewers's reflection in a decorative mirror and realizes they can turn his power against Alma. She and Tristán shatter the glass, and the shards kill Alma, whose body decomposes in seconds. Clarimonde's men then capture them and bring them to a ritual space where Clarimonde sacrifices a bound man and demands they complete Ewers's resurrection.

Montserrat is pushed into a projector beam and enters a liminal space where she meets Ewers. He offers power in exchange for obedience, acknowledging they are alike, both neglected and hungry for recognition. She is tempted but recognizes his manipulation and pretends to submit to buy time.

In the climactic battle, dual projectors screen the film as cultists chant. A pillar of black smoke begins coalescing into Ewers's body. Montserrat draws five runes in blood, then conjures fire as her sixth mark, setting the screen ablaze. Tristán summons Abel's ghost and redraws all six runes on the floor in his own blood. For the final position, where Ewers's personal sigil should appear, Abel instructs Tristán to use "your rune." Tristán draws their childhood signatures, a filled half-moon and a square with an X, overwriting Ewers's system with their own identity and severing his control. Ewers manifests and grips Montserrat's throat, demanding she will him to life. She anchors herself by looking at Tristán and declares Ewers dead, his movie over.

The projectors burst into flames. Ewers's body dissolves, and fire consumes the building. Montserrat becomes lost in supernatural darkness as the last vestiges of Ewers's magic try to hold her. Tristán runs back into the burning building, finds her by voice alone, and they escape together. Two days later, López confirms Ewers's magic has completely vanished, warning that exposure to magic can attract other dangers.

Walking home on the winter solstice, Tristán proposes moving in with Montserrat. After initial resistance, she relents. They negotiate terms with characteristic bluntness: she will not do his laundry or let him drive her car, and he will cook. They walk toward a tamale vendor as a cover of "Don't Fear the Reaper" plays from a passing boom box.