Information / The birth of an army is the first level of Chapter 4.
Second Doctor: Isn't that why we have the Colonel here?
Brigadier Lethbridge-Stewart: Brigadier, now. We need information, information wins wars. Has anyone fought these "Toclafane" before?
Martha Jones: I fought the Toclafane. They had a weakness, was something to do with electricity, but it was so long ago...
Tenth Doctor: Yes! There is a year in human history where the Toclafane decimated the human race, however we were able to destroy the paradox machine which was holding time together, which caused most of the population of Earth to forget the events which had taken place!
Sixth Doctor: Fascinating.
Tenth Doctor: During that year a woman, Professor Alison Docherty, found a way to disable the Toclafane. We need her diary. The diary which should never have existed. And there is only one place in the universe where that is likely to be, the only place a time swept book could ever end up... The Library!
Third Doctor: We're being pulled into another bubble universe!
Seventh Doctor: So what adventures await in this place then?
Second Doctor: You were wrong - this isn't another pocket universe... We've been pulled into the future!