In "The Invisible Enemy", the first adventure of Doctor Who's 15th season, the enemy is all too visible and looks like a giant shrimp. The Doctor (Tom Baker) and Leela (Louise Jameson) receive a Mayday signal, but before they can go to the rescue the Time Lord is infected by the same intelligent virus which has already taken over the crew of a base on Titan. Leela gets the Doctor to a nearby medical station and--while the satellite comes under attack by agents of the Nucleus--miniaturized clones of the Doctor and Leela venture into the Time Lord's brain. The plot thereby combines the classic science fiction tension-builder of a tiny group of humans battling a superior alien foe with the premise of the 1966 film Fantastic Voyage. Inevitably the virus escapes into the full-sized world in a desperate bid to bring about "The Swarming."
This saga boasts copious but variable special effects and laughable makeup; it also marks the debut of irritating robot dog K-9. The Doctor had already been miniaturized in "Planet of the Giants" (1964) and "Carnival of Monsters" (1972). While this 1977 story gets progressively more outlandish and silly, somehow it remains surprisingly gripping to the end. --Gary S. Dalkin