I travelled a lot at the time and the boy and his timid girl were left to their own devices. Carmela still took care of his punishments which he kept secret from the girl. One evening we were due to give him a spanking and secretly invited the girl but told her to hide and watch until I called her. Carmela got him to ask me for a spanking and I had him bare bottom across my knees. The girl watched in amazement at his submission to me and came in to the room. As soon as he saw her he protested loudly and screamed at her to get out. I held him down and proceeded slapping his bum rather more strongly than ever before. Normally he was never hard during a spanking but I felt his penis grow as it hung between my thighs. He was shouting in protest and pain but he was getting really excited. I let him up and he displayed an erection to be proud of. His penis was quite long but not thick and normally formed an arc when he was erect. This time it pointed straight up and was so engorged, I'm sure it was thicker than usual. He was thrusting his hips lewdly back and forth from the pain in his scarlet bottom cheeks. Suddenly he started to come in spurts as he looked down helplessly at himself while Carmela roared with laughter.
He was furious with us for playing this trick on him and mortified that his secret was revealed to the girl. She stood as if she'd seen a ghost. She was frightened by his anger and looked at me plaintively to help her out. He got dressed and left in a huff. We talked to the girl and calmed her down because she was sure he wouldn't see her again. It took a few days and some effort to bring him round, but with Carmela's help, he did and eventually we made peace. The surprise of this event was that the girl was so fascinated by the whole spanking scenario that she eventually took over from Carmela and me.