Tell her to stop

My better, more boring judgement takes over, "Sam! We can't do this." I grab my sister-in-law's arm and pull it out of my underwear, bringing my cock out with it. I'm able to pull her hand off of my cock but my now mostly rigid member is swinging between us.

"Fine, you want to play it that way dear brother-in-law?" She says as she brings her fingers to her hips and begins shimmying out of her panties. "Let's play."

Confused I say, "Sam I told you we can't do this."

She just raises an eyebrow and smiles at me before turning and walking out of the bathroom into the dark quiet hallway. I watch her cute little ass walk away, I wonder what a handful of that feels like, maybe I made a mistake.

That line of thought ends when Sam's voice begins to ring out in the quiet hallway, "Meg! Your ass of a husband..."

Shit, she's going through with it. She going to get me in trouble. Almost instantly my feet are in motion. I run up to Sam and slam into her from behind, one arm wrapping around her midsection the other across her chest with my hand over her mouth. "What the hell! Sam! What do you think you are doing!?" I whisper hoarsely in her ear.

"Mhhmm...." I remove my hand from her mouth. Sam begins to grind her ass back into me, it's at this point I remember she took her panties off in the bathroom and that she pulled my cock out of my underwear. My rapidly swelling shaft is lodged between her thighs. The top side of my shaft is quickly getting wet as my sister-in-law rubs her labia along the length of my shaft, coating me in her juices. "I think," she whispers, "that I'm about to get a good fucking."