It! The Terror from Beyond Space

In January 1973, the spacecraft Challenge 141 crashes on Mars. Six months later, the Challenge 142 commanded by Col. Van Heusen (Kim Spalding) arrives on Mars to rescue Col. Edward Carruthers (Marshall Thompson) and his crew. However, only Carruthers survived and the other nine men have disappeared. Van Heusen is convinced that Carruthers killed his crew to keep water and food for a longer period, and transmits his impression to his crew and the command on Earth. Carruthers denies and tells that a creature was responsible for the deaths on Mars. Before the launching, the creature sneaks in the spacecraft and nobody sees it. Along the journey back to Earth, the powerful creature eliminates one by one the members of the crew that see that Carruthers was not lying.