Colin Baker (The Doctor), India Fisher (Charley Pollard), Michael Maloney (Viyrans/Alien), JJ Feild (David McCallister), Andree Bernard (Ellen Green), Alec Newman (Ed Driscoll), Sam Clemens (Sergeant James Atherton), Alex Mallinson (Soldier Clive), Jess Robinson (Mila)
'So, this is the blue planet you’ve forgotten about. But take another look. You helped us once. I know you can help us again.'
On Earth, civilization has ended and time is running out for the Doctor and Charlotte Pollard.
Will the mysterious Viyrans really help?
'Without you, the human race will die out. And Planet Earth will surely be our tomb.'
(Duration: 120' approx)