With the base facing destruction, the Time Lord and his companions battle to secure the anti-virus. Fifth Doctor adventure stars Peter Davison and Sarah Sutton.
You are at the last episode
See all episodes from Doctor Who
See all broadcasts of Episode 4 (6)
50 years of adventure! Join the Doctor for great clips, trailers, news and fun!
David Tennant, Steven Moffat, Russell T. Davies, William Hartnell, Tom Baker and more ..
Sign in to the BBC, or Register