This happened about six weeks ago. I was in my bedroom getting ready for bed and did not put the light on as there is enough light from the street lights. I was down to my boxers and happened to look across at my neighbours house and the bedroom light was on.
My neighbour is in her forties and not bad looking for her age. She closed the curtains but I noticed a gap of about six inches through which I could see her getting undressed for bed, so of course my boxers were soon off and I started stroking my prick as she stripped off and getting glimpses of her tit's and then her pussy. Just then her husband came into view and he was naked and I could see he was fully erect. Suddenly he came to the window and I thought he had spotted me but he just closed the curtains properly.
I stood there wanking away imagining what they were doing and next thing you know I have shot my load and spurted cum all over the wallpaper. I had to make a dash for the bathroom and get paper tissues to clean not only the wall but also myself. The next morning when I thought of what had occured I was soon hard again and had to have another wank.