| Screenplay by | Johnny Byrne |
| Directed by | David Tomblin |
| Guest Artist | Gay Hamilton |
| Guest Star | Ian McShane |
| Belgium (Flemish) | Levenskracht | |
| Denmark | Livskraft | |
| France/Canada | Puissance de vie | Force Of Life |
| Germany | Das blaue Licht | The Blue Light |
| Italy | Forza vitale | Life Force |
| Japan | True Colour of the Space Freezing Man | |
| Netherlands | Levenskracht | |
| Portugal | A Força Vital | The Vital Force |
| South Africa | 'n Vreemde Lewenskrag | A Strange Being |
| Spain | La fuerza de la vida | The force Of life |
A terrifying force from Outer Space brings freezing death to Alpha personnel. One man has been chosen as the instrument of destruction.
Int. Main Mission
Int. Command Office
Int. Nuclear Generating Area
Int. Zoref's Quarters
Int. Medical Centre
Int. Solarium
Int Technical (clip from Breakaway)
Int. Alpha Corridor
The Nuclear Generating Area set is seen again in Alpha Child.
4 fatalities, Anton Zoref, Hilary Preston, Mark Dominix, guard.
None.
None.
The life force. Not humanoid.

Some prints of this episode (such as the US laserdiscs) show an on-screen microphone top left during the opening shot of Koenig and Bergman. On the DVDs (all versions), the frame is zoomed in so the microphone is not seen. Thanks to James Poll.
Contents copyright Martin Willey