Ring Around the Moon. Season 1, Episode 19. First broadcast Thursday 15 January 1976.

This month, the people of the mythical planet Triton are so (understandably) keen to avoid any contact with the human race that they send a large yellow lightbulb to capture the Moon and issue urgent demands for the entire contents of the base’s OneDrive. These demands mostly involve abducting Helena and inserting things into her brain, giving Barbara the chance to try out a bewildering array of new facial expressions.