Maj. Gordon Towers (William Leslie) and Capt. Dan Webber (Carl Crow) are returning to Space Station X-7 after collecting geological samples and ice from newly-discovered ice caves on the moon. Upon arrival, Dan collapses and is taken to the infirmary by Dr. Hoffman (James Dobson (actor)), and Gordon is reunited with his girlfriend, Dr. Faith Montaine (Dolores Faith), a civilian biochemist.