A prequel to the EA video game Dead Space. Which I don't know anything about.
Alissa Vincent is the chief of security for the Ishimura, a spaceship tasked with recovering a very big and very strange "artifact" from Aeris 7. Once the thing is brought on board, a piece of the planet is hauled up also. And then things start getting weird. The rash of violent behaviours that swept the colony on Aeris 7 are now manifesting aboard ship, as people turn on themselves and each other, committing suicide and murder. A lot of people, including the ship's doctor beleive the artifact is the source, but the captain is determined to complete his mission and bring the thing home. Alissa and her team move through the ship, looking for survivors of this strange plague, but finding only dead bodies and horribly mutated victims. Eventually, Alissa is the only one left standing and, ironically, she finds some reprieve in the shadow of the artifact. She leaves a recording for anyone who might come looking for the Ishimura, then sacrifices herself in a last-ditch, and ultimately futile attempt to save anyone else from suffering the same fate as those on board.
Dead Space the game is rated "mature", so it stands to reason the movie would also cater to an older audience. The film does its best to deliver violence and gore, but the creepy atmosphere is somewhat tempered by the quality of the animation. Be that as it may, the story is well told and rivals similar live action films.
Alissa's sweep of the Ishimura--quiet walks down dark corridors, and violent encounters with Necromorphs--is offset by the drama playing out on the bridge. There, the captain grows ever more unstable as his religious fervour clouds his good judgement. Themes of religious zealotry and intolerance are further explored when Alissa's agnostic/atheist security team meets Irons. Irons is a Unitologist, but he's also straight-thinking, helpful, and fearless. Though some members of the security force are put off by Irons' religion, they set aside their differences in order to survive. Upon the bridge, no such compromises are made.
Unitology is a powerful religion on Earth, and the church's influence is very strong. The Unitologists believe the artifact is the source of life, and it's this belief that brought the Ishimura to Aeris 7, piloted by a captain who is one hundred percent dedicated to the cause. But it's only at the end, when everyone else is dead, that Alissa learns the truth about what the artifact actually does.
Dead Space: Downfall isn't preachy. Most of the film is dedicated to killing Necromorphs, and the story is only meant to fill in the gaps as to what happened before the game begins. And the movie ends right at the start of the game; as Alissa floats through the cold black of space, a rescue ship arrives and hails the now-derelict Ishimura. It's a bit of a downer ending, but the film is a prequel to a story that has a life of its own.