Sharon/Brenda, Fritz + look, but don't touch
Inviting another person into your marital bed was always a risk, but this was one even more so; Fritz knew that from the moment it came up, from the moment Brenda's eyes sparkled in a way he used to be familiar with, a way he only saw when Sharon was around or on her mind.
He sat off to the side and watched as Brenda's hands traced feminine curves, as her lips made a wet path down Sharon's body, and as Sharon writhed beneath Brenda, her back arching and her breath becoming ragged.
Sharon's fingers weaved through Brenda's hair, holding his wife's head to her, moaning incoherently as Brenda fucked Sharon with her mouth and two fingers; neither of them were paying any attention to Fritz as Sharon was brought to her climax, Brenda's name on the tip of her tongue, and the evidence of Sharon's release on his wife's.
Most men would have enjoyed this, but Fritz was watching his wife slip further away from him and closer to Sharon.
Once Sharon rolled them over and pinned Brenda's hands above her head, purring words against Brenda's mouth that he couldn't hear, Fritz was sure they'd both forgotten about him - his presence was just a way to make the two of them sleeping together more acceptable, he realized.