It's the first manned mission to Mars and eight international astronauts set up a small colony with the objective of finding biological life on the planet. The move begins on the last day with less then 18 hours before the mother ship sends a shuttle to pick them up. Vincent Campbell (Liev Schreiber) and Rebecca Lane (Romola Garai) drive a Mars Rover to pick up Kim Aldrich (Olivia Williams) an archeologist. Campbell has a secret that he shares only with Lane: he is claustrophobic (this will be a key point as the plot develops). While not lovers, Campbell and Lane obviously share a bond. Lane is gentle and caring. Campbell is easy-going but pragmatic. They have a lot to do before the departure window and Aldrich stubbornly refuses to leave her dig until she has collected the necessary samples. She is stubborn, insensitive and cold and unpopular with the rest of the crew.
When they all all finally gathered at Tantalus Base, Captain Charles Brunel (Elias Koteas) calls a briefing meeting prior to departure. Aldrich is annoyed that the mission is a complete washout. One of the crew members -- Marko Petrovic (Goran Kostic) believes he has made a remarkable discovery and shows them a culture that shows fossilized bacterial life. He uses this evidence to persuade Captain Brunel to let him make one last attempt to bring back more evidence. Brunel assigns a Rover and crew member Richard Harrington (Tom Cullen) and gives them until sundown to return with the proof.
Things go badly wrong when Petrovic falls to his death in a sinkhole and Harrington cannot save him. Captain Brunel sends out the ship's doctor, Lauren Dalby (Yusura Warsama) to check on both Petrovic and Harrington, who returns to base, leaving Dalby with the body.
When Dalby does not respond to a radio call, Campbell, Brunel and Lane hurry to the site to investigate and Campbell rappels down the sinkhole to find the bodies. They are not there. But he does find evidence of the bacterial life form.
Back at base, Aldrich, Harrington and Robert Irwin (Johnny Harris) are under attack by Petrovic and Dalby whose bodies have been taken over by the bacterial life form and are changing into something else; something that wants to infect and kill the other crew members.
Best part of story, including ending:
The story is cliche. Just another variation on "Alien" and "The Thing" and all those other movies we've seen about aliens invading our bodies so we come back from the dead as killing machines.
Best scene in story:
Campbell is forced to overcome his claustrophobia and scuttle through an air duct connecting two halves of the base so he can contact the mother ship and save the crew. He puts the character to a real emotional test unlike the shoots-em-ups that make up the alien-in-a-human-body attacks.
Opinion about the main character:
He was reactive rather than proactive.