Debbie and I have always had a wicked sense of humour. Practical jokes are the norm and we love to "catch the other out". She is a fun-loving blonde, with long straight hair. She is 5 feet 7, slim, with beautiful 36 dds. One Friday night after I had left the pub, I slowly crept through the garden to where I knew Debbie would be sitting watching tv. (She didn't fancy going out as she had told me she had a tiring week at work). She had texted during the evening to let me know my friend Mason, whom we had last seen months ago had called and said he would pop in as he was driving to Devon and might stop over. I texted back to say I was on the way, an hour later. The house is set in a bushy garden and I sneaked up to the window to peer through, thinking I would rattle the windows to make her jump. Well it was me that got the fright! As I sneaked a peek through the windows, Debbie was on her knees, sucking Mason's cock as he stood in front of her. The cheeky bitch! Mason put his hand to the back of her head as he forced himself into her mouth. Through the slightly open window I could hear as he forced it in, as she gagged and moaned. "You can take more, you slut!" he said and I felt myself going hard as I watched. Deb had never given me any cause for concern before and yet here she was sucking off a friend of mine. I was angry but so horny I didn't want it to stop. I moved to the back door and walked quietly through the kitchen into the hallway. The door was slightly ajar and I watched as Mason forced her to turn around and pulled down firstly her skinny jeans and then her bright red thong, exposing her lovely pink arse. "You've been a naughty slut and you have to pay the price" said Mason as he slapped her hard on the backside. She squealed a "Sorry" back to him, as he pushed her down onto the sofa, forcing her head down and making her arse push into the air. He licked his fingers and wet her arsehole. "You know what's coming don't you?". "Yes" she replied "You". With that she gasped out loud as he forced his large cock into her arse and starting pumping away for all he was worth. I was in shock. I wanted to say something but I couldn't move, I was glued to the scene. Eventually, I came too and decided to edge back out of the house. I made a great deal of noise coming back into the house a minute later, giving them the opportunity to cover up. I poured myself a glass of water from the tap and walked in to the front room. They were both sat as calm as you like on the sofa, although both looked a bit flushed! Mason did stop over that night. I will let you know what happened another time!