Elle stood with her fist inches from the door. All she had to do was knock. Or she could just turn around and walk away. Go back to her dorm and figure this out on her own. But she'd spent the semester trying to figure out this teacher - an older woman who changed the subject wildly from one class session to the next, and graded papers unpredictably. What else could Elle do but ask for help, as much as it felt like admitting defeat? She'd never had to come to a professor's office hours before.

She knocked on the door. It opened - it must not have been completely closed, after all. Elle poked her head in. There was the teacher's desk, just as cluttered with papers as she had imagined it would be, but the chair was empty. Elle checked her watch. Yes, this was the right time. All university faculty needed to post office hours. Maybe she should wait inside.

Elle pushed the door open further, and that's when she saw it. It had been hidden by the door before, but it took up a whole corner of the room - a tall blue wooden box, with a light on top, and the words "Police Public Call Box" in white.

"Holy shit," said Elle.

So the teacher was a nerd. That was the most likely explanation. The kind of nerd who would build or buy her own TARDIS.

Or, said a voice in the back of her head. Or...

No, said the more rational part of her brain. It couldn’t be.

But it would explain why she only has us call her “Doctor…”

Elle stepped forward, put her hand on the TARDIS door, and opened it.