The Fourth Dimension

The Invisible Enemy

OLD FAVOURITE

From this story, the Doctor reverts to using the original, ‘white’ TARDIS console room, including the original console with its moving time rotor central column. The console had been refurbished and a new set was built following the decision to abandon the wooden version of the control room used during the previous season.

HOW MUCH IS THAT DOGGY?

K-9 makes his first appearance in the series. He is said to have been created by Professor Marius as a replacement for his real dog that he was unable to bring to the Bi-Al Foundation with him from Earth due to the weight penalty. At the close of the story, Marius is set to return to Earth and suggests that K-9 should accompany the Doctor and Leela on their travels in the TARDIS.

INCREDIBLE JOURNEY

The sequence of the story in which clones of the Doctor and Leela are miniaturised and injected into the real Doctor’s infected body was very possibly inspired by the film, Fantastic Voyage. The movie, which starred Raquel Welch and Donald Pleasence, told the story of a submarine and its crew being miniaturised and injected into the body of a scientist to remove a blood clot from his brain. As in The Invisible Enemy, the submarine crew have only a limited amount of time to fulfil their mission.

INFECTIOUS CATCHPHRASE

All the victims of the virus repeat the line, ‘Contact has been made’ when they first become infected.

ALSO KNOWN AS

Working titles for this story were: The Enemy Within, The Invader Within and The Invisible Invader.

SOMETHING ON MY MIND

When the clones of the Doctor and Leela encounter the Nucleus inside the Doctor’s brain, it resembles a short black lump with a single eye and a claw. However, when it escapes the Doctor’s body and grows to human size, it has the appearance of a giant prawn!

FAMILIAR FACES

Roy Herrick plays Parsons who works with Marius on the Bi-Al station. Herrick had previously been Jean in 1964’s The Reign of Terror and had also provided one of Xoanon’s many voices in 1976’s The Face of Evil. Frederick Jaeger (Marius in The Invisible Enemy) appeared as Jano in The Savages, Sorenson in Planet of Evil, and Michael Sheard, here playing Lowe, had appeared in three previous adventures and would return in Castrovalva and Remembrance of the Daleks.

THE INVISIBLE EXPERIMENT

The model shots of the vats of the spawning virus on Titan in the final episode were not actually created specifically for The Invisible Enemy. They had in fact been made for a proposed new, colour version of the classic sci-fi thriller, The Quatermass Experiment. However, the project was abandoned and the footage was put to use in this story instead.

DOG BARKER

John Leeson was the actor who provided the voice for both the Nucleus and K-9. Leeson based K-9’s voice on that of philosopher, mathematician and historian, Bertrand Russell.

GALLIFREY

When the receptionist asks Leela if Gallifrey is in Ireland, she replies, ‘Oh, I expect so.’ The notion of the Doctor’s home planet having a name that suggests it’s somewhere in the Emerald Isle had been used in The Hand of Fear and surfaces again in the 2007 adventure, Human Nature/The Family of Blood.

DVD RELEASE

All four episodes of The Invisible Enemy have been remastered and restored and are available on DVD along with K-9 and Company as part of the K9 Tales boxset. The story is accompanied by a commentary from actors Louise Jameson (Leela), John Leeson (K-9 and the Nucleus), author Bob Baker, and visual effects designer Matt Irvine. Also included on the disc are optional CGI effects, the documentary Dreams and Fantasy in which the cast and crew discuss the making of the serial; and original raw studio footage from the studio recordings of the story.