Yet more of the truth comes out -- sorta

"Wait!" exclaimed Martha. "You're serious. You're really not human."

"River" just sneered. "I've been dropping hints as to that for some time now. It's not my fault you're slow on the uptake."

"But why have you been posing as a human?" said Martha.

"Would you believe cosplay?" asked "River".

"Seriously?" asked Martha.

"You humans love to use that word," said "River".

Martha turned toward the Doctor. "Were you aware of this?"

The Doctor said, "I suspected as much when I heard her two hearts beating."

"And when did you hear that?" asked Martha.

"Whenever she started walking real fast," said the Doctor, "Or whenever she watched Clara bend over. I don't remember which."

"And you didn't say anything?" asked Martha.

"Why should he say anything?" asked "River". "He has two hearts as well."

Martha looked at the Doctor with a surprised look on her face. "You mean you're nonhuman too?"

"Actually I'm Gallifreyan," said the Doctor. "And I suspect the good professor is too. Am I right, 'River'? Or should I say 'Rani'?"

"Actually the Rani is a different entity altogether," said "River". "You might as well confuse the Black Guardian with the White Guardian. Or a Cyberman with a Sontaran. But if you really need a name to call me, I suppose 'Missy' will do."

"Missy?" asked Martha.

"As in Mistress," said "River". "Rumor has it I'm a harsh one -- though Clara never had any complaints."

"So is Clara nonhuman too?" asked Martha.

At this point Clara squeaked but no one paid attention.

"I mean, is she Gallifreyan?" asked Martha.

"No, of course not," said the woman who called Missy. "Clara's as human as you are. Or at least she used to be. She's been with me quite a long while so there's no telling how much of me might have rubbed off on her."

Again Clara squeaked but no one paid any attention.

"Why do you keep her naked like that?" asked Martha.

"Aesthetics, I guess," said Missy. "I mean, she is nice to look at, don't you think?"

The Doctor started to say something but he noticed Martha glaring at him and shut up.

Missy continued, "Actually Clara is naked because she made a deal with me. Do you remember the terms of the deal, Clara?"

"Yes," Clara said in a low voice.

"What were they?" asked Missy.

Clara blushed and tried to cover her private parts. "I would go naked like this until you and I rescued the Doctor."

"And did we rescue the Doctor?" asked Missy.

"No, the Doctor rescued himself," said Clara, fidgeting like the Dickens.

"And when I warned you of that possibility, what did you say?" asked Missy.

"That as long as the Doctor was in trouble, I would promise to remain like this," said Clara, repressing yet another blush.

"And what did I say to that?" asked Missy.

Again Clara blushed. "That, by his very nature, the Doctor would always be in trouble. And you were right."