Jamie leapt out of his skin when he turned back to the Doctor, having heard a familiar voice, and saw not the bowtied-pompadoured new-face Doctor but had changed--
Back into his Doctor!
"Doctor!" Jamie cried, happily embracing the little old man. "You're back!"
"What do you mean, 'back,' my boy, I never left!" The Doctor responded by batting Jamie's hands away but taking hold of his sleeve. Jamie stayed near him, trying to determine if this was some kind of trick:
"But, you just--your face, Doctor--" Jamie began. Nikki and Sara had seen him now, too, and looked alarmed, having stepped back, so Jamie felt it his duty to intervene. Jamie, of course, new that the Doctor was a funny old creature, and he was known to change his face sometimes. Jamie did not exactly understand the logistics of it, but it was not quite so queer as if say, he himself changed his face (though that had, in fact, happened, as a matter of fact). He tried to explain this:
"Ach, dinna fret, lassies," he explained. "It's the Doctor! He does this all the time. Well, not all the time--"
"I do what all the time?" the Doctor said grumpily. "Don't fuss me, Jamie, we need to get going--"
"But--where'd the Doctor go?" Nikki asked in a small voice. Sara nodded, dumbly.
"What are you all staring at?" The Doctor insisted. "My word, Jamie, now you've gone and frightened them!"
Jamie's mouth flapped. "But--but--"
"Hush, Jamie, quiet," the Doctor said, going to the controls, and Jamie rolled his eyes and gave up.