The story starts with the retrieval of a capsule bringing back the first soil samples from Mars. The capsule has been damaged and must first be captured by the Canadarm on the International Space Station before the samples inside can be tested. This is a dangerous mission because the crew has never trained for anything like this. Of course they are successful but that is the last of their happy times as they discover that the sample they are set to analyze is deadly to all of them. How each react to this crisis is what makes the movie interesting.
I liked very much that they named the evil Martian cell, CALVIN. Now maybe that name will make a comeback like it should although I do like being unique. I have only met one other Calvin in my entire life and never taught one in 20 years as a teacher.
But all that is beside the point. Soon the alien cell begins to grow rapidly and display definite signs of being a unique creature with a human like ability for survival. The crew soon realizes that the sample needs to be quarantined until they can understand it better. But things have already progressed too far with this little scientific experiment and the inevitable can't be reversed.
From this point on it's a battle for survival when Ryan Reynolds breaks quarantine to save another crew member and puts the whole station at risk with his rash behavior. They try many ways to kill Calvin but none are effective leading to the death of a character I thought would actually make it to the end of the movie.
Soon the creature is loose upon the station and everyone is doomed. Even outside the station, the creature can still live and remain deadly. Clearly these space professionals are totally out of their element and facing something that may be unkillable.
At only 90 minutes and change there is not much room for filler so once the creature goes wild it's all out action until the resolution of the story.
I found the whole experience to be tense, especially in the claustrophobic atmosphere of the station. I am not ashamed to say that this one caused my butt to clench tight for many scenes. But isn't that why we go to movies like this one in the first place? We go to be scared and scared I was and that is what kept me involved from beginning to end. And speaking of the ending, I never saw it coming and I was very satisfied with it. Cool choice.