You could say I was a late bloomer because I'd never had an orgasm before I'd turned 12, but on the other hand I had been masturbated by a girl at 12 which I guess put me at the young end of the spectrum for sexual contact with the opposite sex.

The family was on summer vacation when this all took place. We... my mom and dad and sister Allison and I always took a month during summer and went to mom's folk's cabin in the mountains just outside of Denver. It was a small community called Georgetown alongside the freeway as you leave Denver heading west.

We had been going there every summer for as far back as I can remember and I enjoyed roaming over the hills and fields as a kid. But my sister who was in her teens then hated being pulled away from her friends and "exiled" in the backwaters, as she put it.

Maybe the fact that Allison was board, or maybe because she was 15 and I was 12; maybe that's why we seemed to be fighting all the time that summer. If I said something was white she'd say it was black and then we'd go at it until mom or dad finally broke us up.

So it is even more mystifying that what happened, happened.

I was hiking around up the hill from our cabin, poking around in one of the old ruined gold mines that were all over the place back then, when I heard a noise. I didn't think anyone should be there because it was on our property and trespassing didn't usually happen up here.

I cautiously crept up to the corner of one of the old timber buildings and peeked around the corner. You can imagine my surprise when I saw my sister lying on a blanket frigging herself with her fingers and pinching her exposed nipples moaning softly all the while.

It was the moaning that I'd heard. But it was the sight of my near naked sister that held me there. I was caught in numb confusion, fear and excitement. Up until that moment I'd never seen my sister's naked body before and it was really something to behold.

As I said before Allison was 15, but what I didn't tell you was that she's very popular at school, one of those girls that all the boys wanted to date. I knew that of course and if the truth be told I though she was really pretty too, but she was my sister and I'd never lusted after her like the older boys a school did.

As I stood there trembling, it happened. I guess I moved or something because all of a sudden Allison looked my way and with a cry of surprise she jumped up began screeching at me for spying on her.

It all happened so quickly that I'm not sure I even remember exactly what happened to this day, years later. But my sister was screaming at me, calling me a little perv and threatening me that if I ever said anything to anyone about what I'd seen, she'd kill me.

I guess she was so mad at me that she forgot that she was still half naked. She had taken off her Levis and her shirt was still shoved up over her tits and I could see everything. Everything that a little boy might dream about, but had no real expectation of ever seeing.

Then Allison lunged toward me and the last thing I remember before I turned and ran down the hill at top speed, was my sister's breasts wobbling and the patch of pubic hair between her legs.

That night at dinner there was a palpable tension at the table. Allison wouldn't look at me and I was afraid to make eye contact with her. I mean, I'd seen her playing with herself. I might not have been doing it myself, but I did have a vague idea how it all worked and I knew what she was doing to herself.

It was just too embarrassing. I wished for the hundredth time that I'd left when I first stumbled upon her. But even as I wished it, I knew that I couldn't have, even if I'd wanted to. Watching Allison masturbating was something I'd remember for the rest of my life and I couldn't have cut and run even if I'd really wanted to.

But we had a problem. I guess you could say that I was "one up" on Allison. I'd seen her doing the naughty and she didn't have anything on me quite as bad. I would have promised never to say anything, but she wasn't talking to me, she just kept giving me the cold shoulder for the next few days.

Then about a week later when we'd pretty much gotten back to normal and were talking to each other between fights, she came up to me with sort of a proposition.

I was up by the old cemetery where no one ever went, just walking around and reading the old grave stones. This land was public land but the cemetery was really old and overgrown. I don't think anyone had been buried there for almost 100 years.

When I turned to head back home I stopped short. There was Allison standing about 20 yards away with her arms folded staring at me. She asked me why I'd spied on her the week before and I answered honestly that I hadn't meant to. I told her that I'd heard a noise and had gone to investigate.

Allison seemed to believe me. But we both knew that I had something on her, and when she said, "Tommy, you have to make us even again, I can't have you holding this over me for the rest of my life." I knew then that I'd have to do something humiliating so she'd have something on me.

For some strange reason the fact that I knew it was inevitable, aroused me. I didn't know that I was aroused then, I just knew that I had this excited feeling in the pit of my stomach, and in my crotch. It was a fuzzy defused tension that intensified my awareness of my surroundings.

I mumbled that I wouldn't tell anyone, I promised, but Allison wouldn't accept that. Finally I asked her what I could do to make it okay again. I was tired of all this tension and the strangeness between us. All I wanted was to have everything go back to the way it had been before.

My mouth opened in surprise and shock when my sister said, "The only way to make us even is for you to jack off while I watch you."

I couldn't believe that she'd said it. (I mean, how would you feel if your sister was standing in front of you, seriously insisting that you masturbate in front of her?)

I didn't know what to say, all I could do was mumble, "I can't."

But Allison wasn't going to let me keep my edge over her, she kept saying that it was "only fair" that I do it to make us even. I finally admitted that I was too scared and that I didn't think I could do it.

Looking back from an adult's perspective I am suspicious of Allison's intentions. With time as my filter I now believe that she might have hatched this plan of hers to get even, but also to have the opportunity to see a boy's equipment up close.

Since those days, I've known a lot of women and I think they were just as curios about boys as boys were about girls at that age. And this "set up" was ideal for Allison to learn something about boys without putting herself in a compromising position.