Takes place during episode 2.04, "The Girl in the Fireplace"
Her footsteps were in his mind. All the times the Doctor had listened to the minds of others (not as many as some Timelords, but the Doctor didn't make that sort of thing a habit), no human had ever even thought to open the door to his mind. To reach in. See the darkness.
Lonley then and lonelier now. How can you bear it?**
He didn't answer her---he couldn't answer her---he merely pulled back, sharply. Eyes fixed to hers, a mind he'd seen through and, in turn, she saw through his. He didn't bother covering his emotions as he would've with another person, he had no doubt she already knew them. Shock. Surprise. Awe. Yes, some terror.
"How did you do that?" he demanded. Was she not human? From another world? Her mind said she was Reinette, said she'd lived a life chosen for her from birth. A sickly life, full of unhappiness and loveless matches that the Doctor could only too readily empathize with.
But how...How could she have seen? It was impossible.
** = Dialouge from 2.04 "The Girl in the Fireplace"