"This is not good."  The Doctor looked between his future self and the person who acted like she knew him.  Well, one of him.
"What do you mean, the Doctor?"  Donna demanded.  "Pull the other one, mister!"
"He's me."  The Doctor explained.  "Me in the future."  He turned to the dark-haired girl.  "Who are you, and how do you know me?"  He asked, not angry, just confused.