Missing Memories. (Doctor who fanfiction)

A small girl lay in a field of red grass, her hand intertwine with a small boys. She spoke softly, after a moment. "Theta? What are you gonna choose for your name? after the...Initiation?" the small boy turned his head to her, and smiled brightly, before replying. "Doctor. Because when I grow up, I wanna help people. Hopefully, you, Roxxy.." The girl smiled at this, tears in her eyes. "Then....I'd like to be Miss...like a patient. its subliminal...so it fits in." They both laughed, wishing these days would never end.

If only they hadnt.

The doctor crashes in an underground building, only to meet a girl, who wont tell him a thing about her, not even her name. Only going by the name "Miss" She hides many things from him, and knows many things about him too. But what secrets lie behind those silver eyes. And more importantly, that door no one dares to even glance at?