Mark Harrison slammed the door of the car and trudged across the grass which spread across the wide front of his parent's house in suburban Trentham. It was a hot and sticky night, and he thought better of going inside just yet, choosing instead to sit himself down upon the red brick stairs which led up to the front door, snatching a leaf from the footpath and tossing it away petulantly. His date had been an utter disaster, and Mark's hopes of releasing his sexual frustrations loose at the lithe figure of Caitlin Tanner, the 21-year-old arts student he had been courting at college, disappeared when she pushed his hand away from her breasts and told him to "fuck off."

All hope of getting Caitlin in the sack gone, he had driven her home, stopping at the kerb of her house and, lips pursed and eyes carefully avoiding her, waited until she had gotten the hell out of his car. Fuck her anyway, he thought, the prissy little bitch. She was no virgin, according to friends of his at college, as he sat and wondered what her goddam problem was. Nevertheless, his chances with her were now at an end, and the immediate problem was how he was going to release the aching which had been welling in his balls since his girlfriend Alicia had called it quits some eight months before. His sexual activities in that time had involved only his right hand and a few battered Penthouse magazines, or occasionally a X-rated video tape he had borrowed from a high-school pal and never returned. However he knew this wasnt good enough ... he was 24-years-old and just had to get laid, before his nuts popped.

Deciding against going inside just yet, he stood and walked slowly across the dewy grass, hands in pocket, staring blankly ahead. He got to his car and turned around, leaning against the driver's side door, head bowed. He looked up and scanned around, looking for a distraction from the carnal thoughts flooding his brain, when he saw a light on in the side window, beyond the back fence. It was his 15-year-old sister Amy's bedroom, she was probably in there reading, doing homework, or talking on the 'phone she had talked her father into giving her last Christmas. Mark got on well with Amy ... well, as well as can be expected between a brother and his kid sister, there was no serious animosity between them, but neither were they exceptionally close or confidant in each other. She was a pretty girl with no shortage of pimply faced admirers calling on her or 'phoning her up, but he had never thought of her as pretty, merely acknowledged it to be true.

His neck stretched up as he glimpsed shadows flittering across the light mesh curtain which covered the window - she was moving around the room, he thought, probably cleaning up or trying on clothes or whatever the hell girls her age do in their rooms. He decided to investigate further, just to satisfy his curiosity, and walked softly over the grass, avoiding the gravel path, towards the gate to the Harrison's back yard. Turning the latch slowly and holding the gate up to avoid the creak it made, he slipped inside and replaced the gate, making the barest of noises. He felt a coldness at his ankle, and looked down to see the family's black labrador, Ben, licking his shins and beating his tail against the ground in quick time. Giving the dog a cursory pat on the head, Mark sidestepped it and crept slowly to his sister's window.

From below it he kept an eye on the shadows until he could be sure she was at the far side of the room, then he would raise his head just over the sill and see just what she was doing. That moment came, and as he craned his head upwards and his eyes rose over the level of the window base, he could see Amy taking clothes from her bed, folding them and placing them carefully in her wardrobe.

He watched her intently, his eyes following her form around the room, never missing a beat, when a transformation came over him. She was wearing a thin summer nightgown which came down just over her hips, and he suddenly became aware of the shape of her bare legs working beneath the hem of the gown. And, more than that, there was a small lamp shining from atop her dresser, and when she walked past it the flimsy material of the gown became almost transparent, and he could make out the outline of her slim body beneath the fragile nightdress - her tiny waist, newly flaring hips and, best of all, her small firm breasts which sat high on her chest. And under the starry summer's sky on the damp grass of his backyard, Mark Harrison suddenly realised his sister was a sexually attractive young girl ... and he was becoming hot for her.

He slumped down on the grass, leaning against the wall of the house and breathing erratically as he scolded himself for the thoughts in his mind. 'You fucking pervert,' he told himself, as he attempted to reconcile social taboos with the images of his scantily-dressed sister. However the tingling in his balls overpowered all inhibitions, and soon he was rising again to take another peek at his teenage sister.

She had finished putting away her clothes and was tidying her dresser, as he peered intently into the room, trying to focus upon her and what she was doing. She could not see him, he had realised - it was a dark, moonless night and with the light on in her room, she would not notice her voyeur brother unless she looked long and hard at the window ... and by that time, of course, he would be away. But she suspected nothing, and went about her business ignorant of being watched.

Then, as a strange foreboding feeling washed over Mark has he ogled his sister in her room, she opened the door to her bedroom and strolled out, closing it behind her. He continued to peer in, while cautiously watching from the corner of his eye in case she had seen him and was coming around to catch him in the act. Several minutes passed, and he was about to give up and go inside when the door was flung open and she came back into the room, probably from a visit to the bathroom, he thought. She stepped forward, opening the closet again and taking off a pair of slip-ons she wore around the house, tossing them inside casually. Then, as Mark's eyes widened and his cock hardened almost instantly, his sister faced away from him towards the door, reached down and lifted her nightdress over her head and tossed it in the corner.

Seconds seemed like hours to Mark as he watched, the blood pulsing in his brain. He saw for the first time, beneath her long flowing blonde hair, his adolescent sister's naked back and bare ass as she slipped down the white panties she had been wearing. She stepped forward and fumbled about at her dresser as her brother stared lecherously at her exposed butt ... and it was as fine a butt as Mark had seen, slim and pale as a young girl should be, but with the womanly sweep and fine pair-shape which comes with puberty. As she stood there, Mark's cock became so hard it threatened to burst from his shorts, so he released it with his right hand and began to stroke it slowly, with thoughts of sliding it between his sister's tight little buttocks fuelling his movements.

As he felt the pressure building within his loins, Amy spun around to reach for something beside the bed and unknowingly showed her brother her full naked form. As he narrowed his eyes he could see her breasts, small, pale and conical with even paler large nipples ... he was reminded of his first nervous sight and touch of female breasts, on a date with Sarah McCormick when both were 15 ... but that was nine years ago, and his sister's tits were, he knew, here and now ... and somehow better. His eyes scanned down her flat, white belly and could see the faint trail of blond hair which sat snugly atop her pubic mound. She was not hairy between her legs, but Mark had harboured suspicions of his sister pinching his razors to shave her armpits, so it would come as no surprise if she shaved her pussy. Or perhaps she was not naturally hairy, who knows ... all that mattered was that it was laid bare before him, and he was witness to his sister's nudity.

He fisted his penis quickly as she bent low beside the bed, searching for something unknown and unseen. He could see her small tits hanging beneath her torso, and imagined in the foreground of his mind taking the sweet young nipples into his mouth and biting, sucking, licking ... he wanted to sit Amy on his knee and feast on her breasts, coating them with his saliva and, with his tongue, stiffening the nipples so they rose to meet his touch. And as his balls rumbled and the first signs of his orgasm were felt, his sister stood, faced her dresser and bent down to open the bottom drawer, showing Mark the untouched folds of her cunt through the firm cheeks of her ass ... and the last thought which passed through his brain as his semen spilled out onto the grass, was standing behind his virginal sister and ramming his aching dick into the tight confines of her young vagina.

What Mark was planning was madness, he knew that, but since masturbating to the tune of his sister's nudity, his mind had seem lost in a cloud. He had gone inside, straight to his room and masturbated again, twice, each time climaxing with the image of Amy's bare ass and exposed vagina before him. Four hours had passed, and as the grandfather clock in the front hall chimed 2am, he stood before the door to his sister's bedroom, one hand placed tentatively on the knob as the ramifications of what would happen to him if he was caught floated into his mind. But, as before, his libido got the best of him and he gently turned the knob and drifted into the room like a ghost.

His eyes were attuned to the darkness and he could see, with the aid of the starlight penetrating the open window, his sister's form beneath the white quilt on her bed. She was not awake ... he could make out her light breathing and the rise and fall of the bedclothes. He stood there for what seemed an eternity, watching his beautiful young sister deep in sleep, her fair hair fanned out on the pillow, framing her face. Many times he asked himself what he was doing, and had once taken a retreating step towards the door ... but he was not here to turn back, and moved closer to the bed, kneeling slowly down beside his sleeping teenage sister.

Again he paused, then lifted a shaking hand and placed it gently on her shoulder. She had replaced the nightdress with a light t-shirt before going to bed, and beneath it Mark could feel her smooth flesh, pliant beneath his fingers and the heel of his hand. He left it there for several minutes, as if to test her reaction, but she didnt stir from her slumber. So, braced by this, Mark moved his hand slowly down, down towards the small rise of Amy's right breast, his palm feeling the soft flesh, then the firmness of her nipple as his entire hand rested lovingly upon her tit. During this he kept his eyes on her face, watchful of any reaction, waiting for her to wake and scream in terror ... but there was nothing, just the faint expiration of breath from her lips. Thinking she was deep in a dream, he became bolder and, with the fingertips of both hands, reached down to peel back the sheet and light continental quilt which covered his sister as she slept.

He had to stand to take back the bedclothes, and did it slowly so as not to wake her ... and also to heighten his visual pleasure as he took in the sight of her body, up close this time. Her flat belly was exposed at first, then her navel and tiny waist and, most thrillingly, her lightly-downed pussy ... Mark was thrilled anew to know his sister slept without panties on, as his eyes drank in her genitals and his own became stiff yet again. He took a light step back and stood at the foot of the bed, peering down to drink in the sight of his sister, naked again, but this time without the twin obstacles of distance or the curtain in his way. She was still, in most terms, a little girl ... her body, however, was that of a young woman ... tight, lithe, slim, yet ripening quickly and ready for sex. He stared at her tits and thought of the boys who would one day be thrilled to take one into their mouths, just as he would, given the chance. Or her pussy, sitting delicately between her long legs and lightly covered with the faintest wisp of light brown hair. Her legs were slightly parted, and he could make out the shape of her lips nestled in her pubic mound, and imagined the pleasure that sliding one's cock into this tight little cunt would give. Amy Harrison, his 15-year-old sister, would be the fuck of the century.

Suddenly a heat came over him, and looking at her wasnt enough. Suddenly he wanted to touch ... but knew that doing so would invite trouble, would wake his sister and ignite her screams, would bring his parents into her room to catch him over her naked body, penis hard and hands trembling. The humilation would almost end his life, certainly change it forever. But something overrode all this, cast it from his mind, and he dropped to his knees again, this time near her hips rather than her shoulders.