After learning my penis lack of thickness is the reason for her dissatisfaction, my wife has been secretly fantasizing about a thicker one. She told me her sister doesn't have such a problem since her husband's is thick. I talked to her sister about it, and she came out with a plan. They would come at night to watch movies in our home. She would play the movie and "by mistake" it would be a XXX one. We all four would watch for a while, just enough to get aroused. She would tell her husband she would go to our bedroom, naked, and would wait for him. He would join her and, without turning lights on nor saying a word, he would take her. He would then go back to the living room as though nothing happened. I would ask my wife to do the same. That way, my wife would be taken by her sister's husband without her knowing. As they were in our bedroom, my wife's sister came out of the bathroom and came to the living room. She enjoyed teasing me about her husband making love to my wife. We both heard my wife moaning loudly from our bedroom, so my wife's sister got quickly into the bathroom again. When my wife was back, she told me she loved it and asked me to let her know what type of thing I used to make her feel like that. I told her it was a secret but asked her not to get used to it. I don't know what I am going to do when she craves for it again.