It's not the Doctor, not the proper Doctor, but the next person to appear in the halls of the TARDIS is at least one from her home universe. Andrew knows where he is immediately, but has no memory of how he got there. He simply is, in that way one accepts one simply is when or where or what one finds oneself in a dream. A sense of urgency fills him -- he needs to get to the console room, and he needs to help -- to help who? James? He can't find James, and that's who he looks for as he hurries through the shaking corridors.