The Invisible Enemy (Doctor Who)

093 – *The Invisible Enemy*
093 – The Invisible Enemy
Doctor Who serial
Cast
	Doctor Tom Baker – Fourth Doctor;
	Companions Louise Jameson – Leela; John Leeson (Voice of K9);
	Others Michael Sheard – Lowe; Brian Grellis – Safran; Jay Neill – Silvey; Edmund Pegge – Meeker; Anthony Rowlands – Crewman; Frederick Jaeger – Professor Marius; John Leeson – Nucleus Voice; Roy Herrick – Parsons; Elizabeth Norman, Nell Curran – Nurses; Jim McManus – Ophthalmologist; Roderick Smith – Cruikshank; Kenneth Waller – Hedges; Pat Gorman – A Medic; John Scott Martin – Nucleus;
Production
Directed by	Derrick Goodwin
Written by	Bob Baker; Dave Martin
Script editor	Robert Holmes
Produced by	Graham Williams
Executive producer(s)	None
Music by	Dudley Simpson
Production code	4T
Series	Season 15
Running time	4 episodes, 25 minutes each
First broadcast	1–22 October 1977
Chronology
← Preceded by; Horror of Fang Rock	Followed by →; Image of the Fendahl
	List of episodes (1963–1989)

The Invisible Enemy is the second serial of the 15th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 1 to 22 October 1977. The serial introduced the robot dog K9, voiced by John Leeson. In the serial, an intelligent virus intends to spread across the universe after finding a suitable spawning location on the moon Titan.