A surprise revelation.

Just then, the door opens. You and Amy appear, the latter wearing a suspicious-looking trench coat.

"I guess I owe you that favor," she says, looking at the pair fucking.
"I told you she would," Cathy says with a smile.

Ellen stops fucking Cathy, but doesn't try to get off of her. She's confused, but still submissive.

"I made a bet with the RA," Amy explains, "I bet that you would never submit to her."
"And I knew that you were a submissive waiting to emerge."
"What about...him," Ellen asks.
"When you submitted, he was the one that did this to me..."

You unbutton the coat and pull it off, revealing Amy's naked body wrapped in rope!

"I...had some help from the books she keeps," you explain, "She says that I'm a natural though."
"You are, dear. You have...nimble fingers."
"Thanks. So we had to come see Cathy once she won the bet."
"Pretty sneaky to use Lisa like that, even if for a little bit," Amy says, "But perfectly legal."
"Say Ellen- did your Mistress tell you to stop."
"...no."

Ellen gets back to fucking Cathy's strap-on, while you lead Amy over to the pair.

Cathy and Amy start to kiss, while you feel up the latter's tits.

Ellen cums loudly a minute later, seemingly more-turned on than before.

"So it occurs to me," you say, "We've got two cocks here and two bondage sluts who like to fuck. Shall we share?"