Writer:	Charles Bennett
Director:	Gerald Mayer
Star:	David Hedison (Captain Crane),  Richard Basehart (Admiral Nelson)
Recurring Role:	Del Monroe (Kowalski),  Arch Whiting (Sparks),  Robert Dowdell (Chip Morton),  Terry Becker (Chief Sharkey)
Guest Star:	Alfred Ryder (Dr. Bergstrom),  Don Knight (Sven Larsen)

The majority of the arctic scenes are stock footage from the pilot episode. Note the shot of the snow cat passing the open stage door as seen in that first episode. (edit) Don Knight also worked for Irwin Allen in The Time Tunnel (Rendezvous With Yesterday) and Swiss Family Robinson. Knight was a regular in the 1970 series The Immortal starring Christopher George. He was also very effective as a hit man in the three-part episode of Hawaii Five-O (V For Vashon). (edit) Alfred Ryder previously played the creepy and extremely popular Captain Krueger in the second season episodes "The Phantom Strikes" and "Return of the Phantom". He is also well known for playing Professor Crater in the first aired Star Trek episode (The Man Trap). (edit)

Bergstrom: It has to be friendly. Why else would it contact us? (edit) Alien: You will not answer. Then the answer is with me. You will boil. DIE! (edit)

Uncredited roles:

Paul Trinka (Patterson {aka "Malloy"), Ron Stein (Sonar), Ray Didsbury (Anderson), and Jim Mills (alien voice). (edit) Patterson is inexplicably referred to as "Malloy" by Captain Crane. And in spite of sharing pretty much equal screen time with Kowalski, Del Monroe is credited in this episode, but Paul Trinka is not. (edit) At the end of the first act, after Kowalski and "Malloy" pass out, Nelson, Crane and Bergstrom follow steaming footprints. Suddenly, we see a quick clip of a burnt door closing. This shot is from the ice station XZ-5 during a scene which occurs later in the episode. Also notice, the steam from the footprints is running into the prints. Obviously, the film is being run backward. (edit)

This episode does not have any allusions. Add some now!