Friday somethings happened to me that I can't really explain.I got of work early and went to my wife's work where she works as a storeroom clerk.As is the norm on a Friday the workshop personel stop working just at 14:00 and start cleaning the work area before leaving at 15:00.Now my wife has been intrusted with locking up sometimes so it isn't unusual for her to stay after everyone has left.The security gaurd let me in and since all the door are locked I walked around the building to her office with the intension of knocking on the window so she could let me in.As I peaked through the window I saw my wife on her desk with the new electrician they hired on top of her having sex.At first I was overcome with rage but then something strange happened,in this rage I also felt excitement and felt myself getting a erection.I watched them fucking and going mad on her desk.After a while watching them a saw him increasing his pace before archimg his back and climaxing in her.As he pulled out of her I saw he had no condom on,she quickly took some tissues from her handbag and got up to go to the toilet.My cock was throbbing as I walked back to my car and went home.On my way home I ran over two red lights as my head was running.When I got home I acted as if I knew about nothing,but remember I was still horny.When she arrived abot 45 minutes later I greated her with n glass of wine and a passionate kiss.I lead her to our bedroom and started kissing her and making it obviously clear I had an erection.I don't know if she really wanted to have sex or just not wanted to arouse suspicion she allowed me to penetrate her.As I slipped into her she was wetter than I ever felt her to be before,I commented on how wet she was to which she only smiled.Knowing that what I felt in her was another mans cum made me fuck her harder and longer than before,when I finally came it was like a dam bursting in her.