EXCLUSIVE: A familiar face from the Yellowstone universe appears in the new horror movie Beware Boiúna, and director Mike P. Nelson says the picture takes the genre in a different direction.
Beware Boiúna follows a team of medical professionals who head into the Amazon on a humanitarian mission. Their trip turns perilous when the legendary Brazilian river serpent known as the Boiúna is stirred from its rest, forcing the group into a desperate fight to survive. Leading the cast is Logan Marshall-Green (of Marshals), joined by Kiana Madeira, Jessica Rothe, Jackson Bews, Juan Pablo Shuk, and Vicente Peña.
In a conversation with ScreenRant reporter Liam Crowley, Nelson explained why he chose to strip away the creature’s shapeshifting traits and instead anchor the film in a more realistic framework. He wanted to mix folklore with scientific plausibility, he said, aiming to “blend mythology and science together” so the story feels rooted in both cultural myth and natural history.
Nelson pointed out that much of our storytelling springs from real-world discoveries — for instance, the prehistoric Titanoboa, which lived during the Paleocene. That kind of fossil record allowed him to imagine a scenario in which enormous serpents could plausibly have persisted alongside human communities in the Amazon. By doing so, the director says the film preserves an air of ambiguity: viewers can wonder whether the Boiúna is a spiritual, supernatural presence or simply an enormous animal. He deliberately left that mystery intact, preferring to let the audience weigh both possibilities.
When asked about sequel potential, Nelson seemed enthusiastic about expanding the film’s mythic bestiary. He mentioned other creatures from Brazilian folklore — like the Boitata, described in legends as a horned, fire-breathing snake — as natural candidates for further exploration. Nelson also noted that his research turned up striking visual references online, which excited him about what a follow-up could contain.
Before any sequel can happen, Beware Boiúna must reach audiences: the film is set to open in theaters on October 2, 2026, after a screening at Fantastic Fest two weeks earlier. Beware Boiúna represents Nelson’s fourth feature-length directorial effort; his previous films include The Domestics, Wrong Turn, and Silent Night, Deadly Night. He’s also directed the Friday the 13th short Sweet Revenge along with several other short films.
Marshall-Green, who headlines Beware Boiúna, brings a lengthy résumé to the project. His feature-film appearances include Prometheus, The Invitation, Snowden, Spider-Man: Homecoming, Upgrade, and Carry-On. On television, his credits span The O.C., When They See Us, Big Sky, and And Just Like That….
This year the actor has appeared in two high-profile projects: Christopher Nolan’s The Odyssey, which has amassed roughly $1.7 billion at the box office, and the Yellowstone spinoff Marshals. In Marshals — the fourth series spun out of Taylor Sheridan’s franchise — Marshall-Green portrays Cal Calvin, a former Navy SEAL who joins the U.S. Marshals service seeking a fresh start.
Marshals returns for its second season on CBS on October 4, 2026, just two days after Beware Boiúna’s theatrical debut, meaning Marshall-Green will be prominently visible on screens in early October.
Beware Boiúna opens in theaters Friday, October 2, 2026.
Ava Thornton is an entertainment journalist with a keen eye for the latest in Hollywood, indie films, and streaming trends.
Her work blends insider knowledge with a deep appreciation for storytelling.
