The Invisible Enemy (Doctor Who)

92 – The Invisible Enemy
Doctor Who serial
Cast
Doctor Fourth Doctor
Companion Leela
Production
Directed by	Derrick Goodwin
Written by	Bob Baker and Dave Martin
Script editor	Robert Holmes
Produced by	Graham Williams
Music by	Dudley Simpson
Production code	4T
Series	Season 15
Running time	4 episodes, 25 minutes each
First broadcast	1–22 October 1977

The Invisible Enemy is the second serial of the fifteenth season of the British science fiction television series Doctor Who. It was first broadcast in four weekly parts on BBC One from 1 October to 22 October 1977. The serial is notable for introducing the character K-9, a robotic dog who would become a long-term companion of the Fourth Doctor.

Plot

The story begins with the Fourth Doctor and his companion Leela being infected by an intelligent virus known as the Nucleus. The virus aims to spread itself throughout the universe by taking control of the Doctor's mind. The Doctor and Leela travel to the Bi-Al Foundation, a medical facility in the asteroid belt, to seek a cure.

At the Bi-Al Foundation, they meet Professor Marius and his robotic dog, K-9. The Doctor undergoes a process of miniaturization to enter his own brain and combat the Nucleus directly. Meanwhile, Leela and K-9 defend the Foundation from the infected personnel who are under the control of the Nucleus.

The Doctor successfully defeats the Nucleus within his mind, and the virus is ultimately destroyed. K-9 decides to join the Doctor and Leela on their travels in the TARDIS.

Cast

• Tom Baker as the Fourth Doctor
• Louise Jameson as Leela
• Frederick Jaeger as Professor Marius
• John Leeson as the voice of K-9

Production

The serial was written by Bob Baker and Dave Martin, who were known for their collaborative work on Doctor Who. It was directed by Derrick Goodwin and produced by Graham Williams, with Robert Holmes serving as the script editor.

The introduction of K-9 was a significant development in the series, providing a new dynamic to the Doctor's interactions and adventures. The character of K-9 was designed to appeal to younger viewers and quickly became a fan favorite.

Reception

The Invisible Enemy received mixed reviews from critics and fans. While the introduction of K-9 was generally well-received, some critics felt that the plot was overly complex and the special effects were not up to the standard of previous serials.

Legacy

K-9 would go on to appear in numerous subsequent episodes of Doctor Who, as well as in spin-off series such as K-9 and Company and The Sarah Jane Adventures. The character remains one of the most iconic elements of the Doctor Who franchise.

See also

• List of Doctor Who serials
• Fourth Doctor
• Leela
• K-9
• Doctor Who (season 15)