This is really great stuff. Bringing Sarah into the picture seems to balance things out. She challenges S in a new way and brings some strength to the submissive side of the picture. I love it that S is falling for her, but if he wants to keep her, he has to stay tough.

We're also getting more inside S's head--his thought process as he figures out what to do next.

Sarah, hearing and seeing this, got more turned on and moaned in her own rhythm. Idea.

“Lynn, you may NOT come until Sarah does.” I said.
I love this. Totally spontaneous. "Idea" is brief and straight to the point, and reveals S without interrupting the action.

Can't wait for more!