The combined knowledge of humanity is conveniently stored on microfilm, but Brundlefly would rather just eat it.
Brand new companion, Harry Sullivan, messes with the helmic regulator aboard the TARDIS and sends himself, The Doctor and the old girl Sarah Jane Smith to a cryogenic repository holding the last remnants of humanity.
The Ark, as it is called, has been orbiting the Earth for millennia now. Tragically, its passengers overslept as a race of flesh-eating and mind-absorbing space flies stowed away and turned off their alarm clocks to eat them in their sleep.
It’s now up to The Doctor and his two friends to rescue mankind from certain extinction.