A second mission to mars arrives at the red planet to discover the fate of the previous crew sent there. Only one is left alive, the rest were killed by some creature... according to the survivor who is not believed and taken back with the to stand trial for multiple murders. It seems he wasn't lying afterall when the creature is discovered to have made it's way on to their ship and is now travelling back to earth with them and killing the crew along the way.
This film is certainly a low budget product of its time but does have good points. One of those isn't the monster, however. it's pretty ridiculous looking. The acting isn't great and neither is the writing... what's left? The effects of the ship are fairly well done and some of the shots are well thought out. It made me realize how much can be told by one shot and not need further explanation. An example if this is when the nurse disconnects a bottle of blood from a patient injured by the monster, she puts it on a table and there is a shot of the table with about 10 more empty bottles and it tells you right away there is a now a shortage and the treatment isn't working. The basic setup is also interesting and will remind filmgoers of "Alien" as the the ship is divided into layers separated by hatches and the deadly Martian comes from them floor by floor, hiding in ducts and picking off the crew one by one.
Not the best or the worst of this sort of 50s sci-fi so something to watch if you happen to catch it and can deal with the acting.