Between my second and third year of college, I worked with a summer custodial team for the college to prepare the dorms for summer groups. As this was not always a busy job, often we had spare time before the end of the day.
One of these days I found a Harlequin romance novel and started reading. I was off in a corner so I think I was alone, but nearby was another student worker. She too was skimming a book and waiting for the end of the day.
As I got into the book, it became more exciting and I felt myself getting harder and warmer. I began to stroke slowly through my shorts and carefully watching not to get caught. It was so exciting to be so close, but still made me nervous. Would I be caught? This just made the experience more and more exciting. Did she know? I don't think so, but was never sure. I did finish both my book and my stroking with a sense of accomplishment.