'The Infernal Machine' by Anthony Terpiloff and Elizabeth Barrows

A strange spacecraft which seems to defy the laws of physics lands on the lunar surface near Moonbase Alpha. After hearing a voice appealing for help, Commander Koenig, Doctor Russell and Professor Bergman reluctantly accept an invitation to visit the craft. On boarding the ship they meet an old man known as 'Companion', who requests supplies for Gwent, the owner of the voice. Gwent is the spaceship, a living, thinking cybernetic entity. Doctor Russell realises that Companion is dying, and requires urgent medical attention; however, when Gwent refuses to allow them to leave, Companion collapses and dies. Gwent becomes furious, blaming the Alphans for the death of the old man - it decides to imprison them and make them take Companion’s place...

Martin Landau (Commander John Koenig), Barbara Bain (Doctor Helena Russell), Barry Morse (Professor Victor Bergman), Nick Tate (Captain Alan Carter), Zienia Merton (Sandra Benes), Clifton Jones (David Kano), Suzanne Roquette (Tanya Alexander), Leo McKern (Companion / Voice of Gwent), Gary Waldhorn (Winters), Sarah Bullen, Loftus Burton, Andrew Dempsey, Michael Stevens, Andrew Sutcliffe (Main Mission Operatives), Tony Allyn, Quentin Pierre (Security Guards)

Directed by David Tomblin
Produced by Sylvia Anderson
Series created by Gerry and Sylvia Anderson

TX:
UK (ATV Midlands):
January 8th, 1976

Notes:
*Featuring Commander John Koenig, Doctor Helena Russell, Professor Victor Bergman, Captain Alan Carter, David Kano and Sandra Benes