A spaceship from Earth is sent to look into the possibilities of colonizing Mars. The two astronauts however are attacked by an unseen entity and disappear. Three years later a new expedition of four men is sent led by Adam West to discover what happened and find the remains of the old ship. As figured, they start getting knocked off one by one by the same unseen enemy, however they soon make a shocking discovery of who or what is attacking them. This is a pretty ok episode that I loved to watch especially when I was younger. Watching it know it's easy to see its faults, as a lot of what's happening could probably be avoided by the characters who are supposed to be trained military astronauts not making stupid decisions. The creature on display however is pure 50s b movie gold and is why this is getting the rating it is as it's pretty much the only memorable thing about this, that and of course starring a young pre-Batman Adam West. The original short story this was based on sounds a lot better than how this turned out, and after finding out the script was re-written multiple times it's not surprising.