--Scott's POV --
"YOU LEFT YOUR FRIEND, AN UN-MATED OMEGA, GUARDED BY AN UN-MATED ALPHA?!?" Boyd shouted.
Oh no. Scott's eyes widened in alarm as realization dawned on him, then he took off running through the house and yanked opened the basement door. He ran half way down the steps, but then caught sight of the room below.
Stiles was on his hands and knees on the couch, with Derek Hale plastered over top of him. Their clothes were still on, but both had their pants around their ankles. Scott caught an eyeful of flexing ass, as Derek kept making small humping motions, grinding his knot as deep as he could within Stiles. Stiles kept making pathetic little whimpering noises, while Derek made growling noises around his teeth which were sunk into the junction of Stiles' shoulder and neck.
Well, shit. They were already mated. There was nothing to be done now except let it run its course. Derek would probably need to mount Stiles once or twice more before he was satisfied. It was very dangerous to approach a recently bonded alpha/omega pair, especially if you were an alpha like Scott.
Scott quietly tiptoed back up the stairs, and shut the basement door behind him.