The Doctor, now alone in the TARDIS, sits in his chair and has another (sadly missing) monologue.
DOCTOR: Even after all this time he cannot understand. I dare not change the course of history. Well, at least I taught him to take some precautions. He did remember to look at the scanner before he opened the doors. Now… they’re all gone. All gone. None of them…could understand. Not even…my little Susan…or Vicki …and yes … Barbara and Chatterton… Chesterton! They were all too impatient to get back to their own time. And now… Steven. Perhaps I should go home, back to my own planet. But I can’t. (Upset.) I can’t.
(Transcript via ForeverDreaming)