Hungover and exhausted from a party the night before, Col. Foster reports for a scheduled fitness program at the SHADO health farm. While relaxing in the sauna, Aliens invade the building and kidnap Foster. He is taken aboard their ship, put in an Alien uniform, and converted over to liquid breathing. As the UFO escapes, Captain Waterman in Sky One is unable to shoot down it down, as he knows Foster is aboard. However, he does damage it to the point where it cannot escape the lunar gravity, and it eventually crashes on the Moon. Miraculously, Foster survives the crash and is taken back to Moonbase. However, he is still breathing liquid -- will the Moonbase staff and its crude medical facilities be able to convert him back to normal breathing without killing him?