Alpha Child. Season 1, Episode 7. First broadcast Thursday 16 October 1975.

An eerie green glow is making for Alpha, bringing with it the most terrible consequences, as the first baby born on the base undergoes two periods of ultra-rapid growth, becoming in mere seconds a terrifying English moppet and shortly after that Julian Glover in a skimpy miniskirt. Is this the next stage in human evolution, or merely an invasion by an alien who wants to give his mother a nice makeover and a good rogering before (inevitably) killing everyone on the base?