I met Suzi in college; she was a sophomore and I was in my senior year. She was perky and delightful, I fell for her like a ton of bricks. And I was lucky that she fell for me as well.

We've been together ever since, now I'm twenty-six and she's twenty-four. We've lived together since about six months after we'd met and now were living in a home we had bought together, pretty much equidistant from where each of us worked.

Like so many couples, sex was always an important part of our life and that hadn't diminished a bit since we began working. We have sex nearly every night of the week and usually twice a day on each weekend or holiday.

Suzi always liked our lovemaking to happen with the lights on; she also had me install a mirror on our bedroom wall so she could turn her head sideways and watch us in action.

It was during a particularly energetic fuck on a Saturday afternoon when she said, "Just keep doing what you're doing, don't look back, but I think I see our next-door neighbor watching us."

"Well, she's getting a good show, you really seem turned-on today," I panted as I thrust back and forth as she pulled her legs back against her chest putting her pussy up for me to take long, slow, deep strokes down into her.

"I'm sure I can see her, it looks like she's standing there masturbating while she watches us."

"Maybe she'll learn a thing or two, huh?"

"Oh, shit, this is turning me on having her watching us fuck like this. God, let me get up on you, I want to do you reverse cowgirl so maybe I can see her better," Suzi said and I moved off her and laid down while she squatted down between my legs reaching under for my cock as she sat back down driving me up into her.

"I don't think she knows I can see her but she is masturbating back away from the window some. That I can make out."

Well, Suzi fucked me hard, putting on a good show for our neighbor who, by the time we had finished, seemed to be gone from the window.

We knew her, of course, her name was Sharon Walker and she was a few years older than me, probably around thirty.

Sharon was a teacher, elementary school, I believe, and was single. She was attractive, not beautiful, but nice-looking, and fairly tall, probably about five-nine.

Her hair was shoulder-length, kind of dirty-blond and straight with bangs in the front. Her figure was slender and she did have nice boobs that did rate some noticing.

It was what happened on Monday that really changed things.

When I got home from work, on my way into the house, I grabbed the mail and tossed it on the kitchen table then went back to change.

In the meantime, Suzi had gotten home and came in the bedroom holding an envelope.

"Look at this, no postage. It's addressed to you and me. Should I open it?"

"Well, it could hardly be a bomb, Suzi, maybe we've won the lottery. Sure, open it."

She pulled the flap open and took out a small notecard.

"It's from Sharon, next door," she said as she began to read.

"'Dear Suzi and Tony, ' she says, 'I saw the two of you having such wonderful sex the other afternoon through your bedroom window from mine, I just wanted you two to know how exciting it was to watch. It has given me many wonderful climaxes of my own as I've imagined myself there with the two of you.'"

And it's signed, "Thanks, Sharon."

"Wow, we have a fan, huh?" I said laughing.

But Suzi wasn't amused, saying, "'I've imagined myself being there with the two of you.' It sounds like she's fantasizing that she'd like to join us?"

"Hmm, yeah, I guess it does."

"What do you think? I say we should invite her in."

Now you don't know Suzi like I know Suzi, as the old song goes, but my wife had several girlfriends in high school and college along with a number of boyfriends as well. She's never made it a secret that she likes sex from either side of the fence.

It's something that has never bothered me, I'm not the jealous type and if she would like to have some fun with our next door neighbor, it was making my cock hard thinking about getting my own share as well.

I was standing there in my boxers, now all tented out, as she said, "You're kinda giving away that you're interested if I'm reading this correctly," as her hand reached out and gripped my erection.

"So, maybe we should see if she'd like to join us?"

"I think we're both interested and it seems fine with me. How do we go about doing this?" I asked.

"Well, she obviously put this in our mailbox so we would know how she felt and to give us the idea of her joining us, so I think we should just go over and see her and ask her to join in. Why make it complicated?"

"Do you think she's interested in having fun with us both? Kinda sounds that way, huh?"

"To me it does," Suzi said and we agreed to change and go over and see if she was home.

We walked up her front porch steps and Suzi rang the bell.

A minute later, the door swung open and there was Sharon, a bit red-faced, looking at us.

"Um, I guess you got my note. I hope you're not mad."

"No," Suzi said, adding, "Could we come in?" and Sharon moved aside letting us into her house.

We went into her living room and she sat down on the sofa. Suzi sat next to her and I sat across in an easy chair.

"We wanted to tell you that we don't really mind if you watch us having sex. Tony and I are pretty open about those kinds of things and we think it's fine if you want to watch."

"I really didn't intend to watch you the other day but you two really were beautiful to see and, well, I just got caught up in watching you. I'm glad you aren't upset about it."

"No, we really kind of liked the idea that you watched us, we don't mind at all," I told her.

"Well, that's good, I do want to be a good neighbor."

"You did say something about being there with us," Suzi mentioned.