'The Doomed Planet' by Alan Fennell

Fireball XL5 narrowly misses destruction from a planet that has broken out of its orbit. When Professor Matic realises that the uninhabited world of Memboro also faces destruction from the rogue planet, Steve Zodiac takes XL5 there to ensure that it really is devoid of life. Memboro does indeed seem deserted, although the XL5 crew get the feeling they are being watched. But on returning to Space City, Steve and the others are unaware that they are now being followed by a mysterious flying saucer…

Paul Maxwell (Colonel Steve Zodiac), Sylvia Anderson (Doctor Venus), David Graham (Professor Matt Matic / Lieutenant 90 / Zoony the Lazoon), John Bluthal (Commander Zero / Saucer Man), Gerry Anderson (Robert the Robot)

Directed by Alan Pattillo
Produced by Gerry Anderson
Associate Producer Reg Hill

TX (UK - ITV):
8th April 1963

Notes:
*Featuring Colonel Steve Zodiac, Venus, Professor Matt Matic, Commander Zero, Lieutenant 90 and Robert the Robot