Does my Boss Masturbate at Her Desk?

I have a new job. Big office, several workers. And, being the new one, almost every day I stay late, to the point all my coworkers are gone. Almost all. There is this woman. Several years older than me, maybe fifty-something. Not what you would call hot, although she was fine. Not that I had ever looked at her in a sexual way, she was a superior, although I'm not even sure where she stood in the company (she had her own office, although the walls were crystal and I could see her work).

One day, already almost alone, I was chatting with a friend, and she suggested I masturbated at work, just because the idea turned her on. I said I was not alone, I was always almost the last one, but my boss always stayed later. And my friend answered "maybe it's her who waits until you leave to masturbate at her desk".

Since that day, I can't take the image out of my head. Every late evening, when it's just the two of us, I imagine her touching herself under the desk. Or desperately horny, and desperately waiting for me to leave. I'm obsessed with her, now. I don't even want to do anything with her. Just to see her all by herself. Maybe if I casually turn off the lights and work in the dark she'll think she's alone and I will get a glimpse?