My encounter with a younger man (best sex of my life)

The story begins about 3 years ago. I was living in an apartment and my friend, Audrey, had just moved in to the apartment next to mine. Audrey was a single mom with a 1 year old daughter. She was 22, quite a bit younger than me as I was 31, but none the less, living next door and sharing walls, we became very close. Audrey had a friend she worked with named Nick who had just graduated high school. He was about 6ft tall and a had a stocky, strong build. Nick would go over to her house almost every day. Sometimes she would leave and Nick would watch her daughter. He was a great guy and would do anything for Audrey. I began to wonder if they were hooking up or just really close friends. One night Audrey and I went out for some drinks and after we’d had a few I asked her if she had a thing with Nick. She immediately denied and laughed it off. “No way! He’s like my little brother!” she said. So I shrugged it off and believed that was all there was to their relationship. A couple weeks went by and Nick was still going to her house almost every day. One night, I was in my bedroom, which by the way shares a wall with Audrey’s bedroom, when I kept thinking I was hearing a faint moaning sound. I turned the tv down and listened closer. The moaning, clearly a woman, got louder as the seconds ticked by. I ran to look out the window and saw Nick’s car in Audrey’s parking spot. I went back in my bedroom to listen again, trying to decide if it was just her tv a little loud. But then I started hearing a thumping noise. Like a headboard hitting my wall from the other side. The moaning got louder. I knew what was going on. Nick was fucking her brains out.