3. MacGuffin!
The reason for all this stuff! The thing characters have to hunt down! Maybe how the Doctor ended the Time War, judging by Hurt's expression.
So, he's there alone, it seems--but in another shot, we can see what looks like Rose's hair across the pedestal from him. So why is Rose there alone with John Hurt? This incarnation of the Doctor was so removed from his time stream, so secret, that when Clara richocheted around the past and the future she was still surprised to find him. How would Rose know about him? Even River didn't know about this guy. And why is this area so run down and deserted? I mean, it doesn't seem like a logical spot to hide something that could exterminate species from time itself. Is it maybe the remains of some ancient war? Also, we know from a new picture that all three Doctors will stand around this. Maybe this is the key to ending the Time War, but for some reason it takes all three Doctors to do it? And maybe Rose too, if she's the Bad Wolf? So, what's this thing? They have to go find it. The Doctor went to find it alone, in his Tardis, and walked across a desert. Why did he need it? Is this before or after the three doctors meet? What's this thing and why is it so important!