Sunbathing
Peter knocked loudly at the door for a second time. Still no answer.

"I could have sworn they told me they'd be home", he thought. "Must be round the back"
He trudged around to the side gate of the house and reached over to unlatch it, hopeful there were no spiders lurking in the leafy path that stretched down the side of the house to the backyard.
Peter lugged the bag full of fresh vegies he'd cut from his garden across the street and made his way to the back of the house.
He didn't call out, as he thought his friends Doug and Liz might not be home, and figured he'd leave the bag on their back doorstep.
Reaching the corner of the house Peter stepped into the sunshine once more and was confronted with a stunning sight.
There was Liz, spreadeagled on a beanbag on the deck, completely naked except for a straw hat covering her face.
Peter stared in amazement. He'd always fancied Liz, and there had been a hint of sexual tension in the air for some time, but he hadn't expected to ever see her body, despite his fantasies.
She'd obviously been in the pool recently because there were small droplets of water on her thighs, but Peter was more captivated by the neatly trimmed bush surrounding a very full and inviting pussy mound.
His eyes travelled up Liz's body to her full breasts, where two quite erect nipples pointed skywards, invitingly. Peter's loins began responding, and he cursed that fact that he had on only loose shorts. His cock pulsed inside his pants and began to grow, despite his horror at what was now turning into an erotic scene, rather than an accidental exposure.
Peter couldn't tear his eyes away. He viewed the soft skin of her inner thighs, the flesh of her belly, and the inviting crease at the top of her pussy where her clit was hidden. He found himself imagining his tongue exploring that fold, searching out the nub of pleasure that lay within.
His mind played tricks and he could almost feel her pussy lips spreading apart for his invading tongue. Next his fantasy spread to Liz's juicy melons, where his tongue circled and toyed with her hard nipples, cold on his lips from their dip in the pool. He could feel her now wet cunt slide around his dick as he lowered himself onto her, and without realising it, had begun to gently rub his cock through his shorts. The imagined moans of Liz as her lips grazed his ear, and his own grunts as he began to thrust his rod inside her made him even more excited, and he could almost feel her wetness coating his shaft.

In an instant Peter's eyes sprung wide open, as he heard a voice behind  him;
"She's awesome isn't she? How are you mate?"
It was Doug, who had silently approached from behind Peter, who jumped with a start, which in turn roused the previously oblivious Liz.
"oh...er...um...yeah...well...um...just stopped by......vegies......" stammered Peter as he tried in vain to hide the stiff prick now all but protruding from the leg of his shorts.
Liz, for her part, looked a little embarrassed, but she caught a glimpse of Peter's now hard cock and smiled wickedly.
"Enjoy the view, Pete?", she asked, resting back on her elbows, now making no attempt to cover herself up.
"Shit", said Peter, "I am so sorry. I didn't mean to offend. It was so unexpected and my mind just got carried aware so I was staring, and..."
"I think that's not all you were doing by the look of that thing", said Liz, eyeing off Peter's slowly deflating cock.
Peter shuffled his feet nervously, and hefted the bag of vegies, hoping for a change of subject.
"Some cucumbers and tomatoes in here for you guys. I'll just leave them. Again, I'm really sorry if you're offended. I'll just go."
"Don't be silly," admonished Liz, "Stay for a drink at least - it's pretty warm. No harm done."
After a little convincing Peter agreed to a drink in the shade by their pool, and soon Liz and Doug began to tease Peter about his poolside hard-on.
Peter blushed, especially when Liz asked what he was intending to do with it anyway......
Peter figured what the hell and told a slightly condensed version of his fantasy as he'd stood there.
Liz cast a glance at Doug, who smiled back at her, and with that she rose, took Peter's hand and began to lead him inside the house.
"I think we should go in out of the heat," she said, casting a sensual glance over her shoulder at Peter.
Peter followed, a familiar stirring in his loins occupying his mind, as Liz's sashaying arse occupied his eyes.

As for what happened inside - more in part two.