The Invisible Enemy (Doctor Who)
A sentient virus threatens the universe from Titan.
The Invisible Enemy is the second serial of the 15th season of the British science fiction television series Doctor Who, first broadcast in four weekly parts on BBC1 from 1 to 22 October 1977. It is notable for introducing the robot dog K9, voiced by John Leeson. The story involves an intelligent virus seeking a spawning location on the moon Titan.
Quick Facts
- Number
- 093
- Serial name
- The Invisible Enemy
- Doctor
- Tom Baker – Fourth Doctor
- Companions
- Louise Jameson – Leela; John Leeson (Voice of K9)
- Director
- Derrick Goodwin
- Writer
- Bob Baker; Dave Martin
- Script editor
- Robert Holmes
- Producer
- Graham Williams
Facts from the source article.
Plot
Human space travellers cruise near the outer planets with their ship on autopilot. The TARDIS travels through the same region, and both crews are infected by a sentient virus. The virus chooses the Doctor to host its mind, the Nucleus of the Swarm, which declares Leela a reject and orders her killed. The Doctor breaks free of the infection and directs Leela to take the TARDIS to the nearest medical centre. There, Professor Marius introduces K9, a robotic dog he built to replace a real dog left on Earth. Leela and the Doctor create clones of themselves, which are shrunk and inserted into the Doctor to destroy the Nucleus and escape through a tear duct. Meanwhile, Leela and K9 fight infected hospital staff. The plan fails, allowing the Nucleus to escape and become human-sized; it and the infected staff leave for Titan Base to spawn. The Doctor realises he is cured because Leela's clone introduced her immunity factor into his bloodstream. He replicates the cure for Professor Marius, and the Doctor, Leela, and K9 proceed to Titan Base in the TARDIS. They fight infected humans but lack sufficient weaponry to destroy the Nucleus or its hatching macro-sized children. The Doctor jams a door, rigs a gun to fire into a cloud of oxygen gas, and escapes. When the Swarm forces the door open, the blaster ignites the oxygen in Titan's methane atmosphere, destroying the Swarm and the base. Back at the hospital, Professor Marius offers K9 to the Doctor, who accepts, and the Doctor and Leela leave with their new companion.
Production
Before K9 was confirmed as a recurring companion, the story went by several working titles: The Enemy Within, The Invader Within, and The Invisible Invader. The choice to keep the robot dog for multiple serials came late, partly to justify the high cost of building the prop. Filming and recording took place in April 1977. A visible crack in a wall appears just before K9 fires at it; the flaw had been hidden originally, but a reshoot left no time to fix the seam. Michael Sheard, playing Lowe, made his fourth Doctor Who appearance here, following roles in The Ark, The Mind of Evil, and Pyramids of Mars. Brian Grellis, who had played Sheprah in Revenge of the Cybermen, later returned as the Megaphone Man in Snakedance. Frederick Jaeger, as Marius, had previously appeared as Jano in The Savages and Professor Sorenson in Planet of Evil.
Broadcast and reception
The story was repeated on BBC1 on consecutive Thursdays from 13 July to 3 August 1978, with ratings of 4.9, 5.5, 5.1, and 6.8 million viewers. Stanley Reynolds of The Times gave a generally negative review after the second episode, noting that in ITV regions competing with Man from Atlantis, the series was losing the ratings war. Later reviews were also not positive. Paul Cornell, Martin Day, and Keith Topping in The Discontinuity Guide (1995) called it an ambitious project that looked like a grand folly due to budget and script, though K9 made an impressive debut. David J. Howe and Stephen James Walker in The Television Companion (1998) deemed it one of the weakest Fourth Doctor stories, consisting of clichéd action-adventure material with inconsistent visual effects. Mark Braxton of Radio Times (2010) awarded two stars out of five, contrasting it with the Philip Hinchcliffe era and calling it a kidified, Poundland Star Wars; he praised some effects and Barry Newbery's design but criticised action scenes, lighting, and white sets, and noted Louise Jameson looked ill at ease despite her usual effort. DVD Talk's John Sinnott disliked K9's convenient use and found the plot too similar to Fantastic Voyage, though he praised the visual effects inside the Doctor's head.
Commercial Releases
A novelisation by Terrance Dicks was published by Target Books in March 1979. The story was released on VHS in September 2002. The DVD was released on 16 June 2008 as part of the double pack K9 Tales with the spin-off K-9 and Company. It was scheduled for release in Doctor Who DVD Files issue 133 on 5 February 2014. In March 2024, the story was released on Blu-ray with new special effects as part of the Season 15 Doctor Who - The Collection Box Set.
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