"To find the derivative of something like x^3, take the exponent, put it at the front, and subtract one from that exponent. That'd be 3x^2," a voice said in the back of Elen's mind. 16-year-old Elen Cavendish sat in Intro to Calculus, half-listening to the teacher. Finding herself utterly unable to concentrate on the teacher, she turned her attention to more interesting things; like drawing people, flowers, and whatever else came to mind in her notebook. The boredom of sitting still for the last hour filled her mind. The only redeeming thought was that it would be over in just five minutes, then she could go home.

"Why is everything in my life so boring?" she thought to herself, "I wish I had a little spice in my life." Elen had plenty of friends, but in her small town of 1,500 people, there wasn't much to do with them. Hanging out was only interesting for so long.

Elen was shaken out of her thoughts by the ringing of the bell. Freedom. She packed up her belongings and stuffed them into her backpack. She didn't have any homework, but she always brought her books home anyway, just to make her parents happy. Going out into the hall, she lingered in school a moment longer to make conversation with some of her friends and to be hit on by a couple of boys. Boys had taken an interest in her ever since she hit puberty. Her slim, shapely figure and early development of her breasts had made her a hit with the opposite sex. Add in silky-smooth, bright blond hair and cute face, and what do you get? A very sexy girl.

Elen reciprocated, too. She even had had sex several times with one special boy, John. He moved away last year. Since then she simply didn't have the urge to do it with any of the other boys at her school anymore. Elen had always been one of the most intelligent and mature students at her school. This actually posed a problem for her sex drive, since she simply couldn't bring herself be interested in an immature or intellectually inferior boy. She appreciated their attention, though.

With nothing else to do around school, she left and headed for home. Since her town was so small, in both size and economy, the school district didn't offer transportation, so everyone had to either provide their own ride or walk home. For her it was a two-mile, half-an-hour walk. Her typical route followed roads most of the time, but took a shortcut through a field with high grasses.

Half way through the field Elen spotted a dog in her path. It was a large German Shepherd. It didn't make any aggressive moves towards her or growl, so she didn't feel any danger. Taking a closer look, she noticed it didn't have any collar on, thought its fur looked clean and well kept.

"Hello, boy," she said in a soft, calming voice, "Where did you come from? Are you lost?"

Elen had always had a deep compassion for animals, and her heart went out to the big dog. Surely it had a home to go home to. She slowly made her way over to the dog, being careful not to spook him. The entire way she tried to sooth him by talking to him softly, and holding her hands out invitingly. Her efforts were rewarded: she got all the way to him. He didn't run away or growl in warning.

"Are you someone's pet, boy?" she cooed as she petted him.

While she stood there petting him and talking to him softly for some time, Elen thought about what she should do with him. She couldn't take him home, since her parents had no tolerance for pets of any kind. She couldn't take him to an animal shelter, since her town didn't have one.

Her thoughts were abruptly interrupted when the huge German Shepherd leapt up at her, licking her face and knocked her onto her back. Since it was May, it quite warm, and Elen wore a short skirt to school that day. Now that skirt rode up around her waist, and her legs reflexively spread to help her try to break her fall. The dog took this opportunity to access her pussy, which was now being covered with only a thin layer of cloth. Startled, it took her several seconds to realize what he was doing.

"Bad boy! You can't lick me there. That's wrong. Stop," Elen cried.

He either didn't understand her or didn't care. He just kept on licking her crotch through the panties. Instinctively, she closed her legs. The huge dog growled in response.

Realizing that he could probably kill her with a single bite to the neck, she fearfully opened her legs. He immediately resumed his licking. It didn't take long before her panties were soaked with his saliva. Elen was very scared, and had no sexual interest in dogs. Despite her lack of interest a desire began to stir deep within her. He began to lick her panties into her pussy lips. She couldn't deny that it felt great.

"How long is this going to last?" She asked more to herself than to him. Moments later, he dexterously grabbed hold of her panties with his teeth and tore them open. Amazingly Elen was totally unharmed. Now with her privates exposed and vulnerable she finally made her realize what he was about to do. This was not going to end any time soon. He wanted to be satisfied. Horrified, Elen began to back away from him. A loud growl and a gentle but pain nip on the leg let her know that he meant business. She stopped dead in her tracks.

He now had full access to her vagina. He greedily started licking all around and even into her hairless pussy. The rough wetness of his tongue rhythmically scraped against her clitoris. If she wasn't aroused before, she was now. Every fiber of her being knew that this was wrong, and yet her primal instincts still couldn't resist the sexual stimulation this animal was providing her. Elen began to pant and moan under his continued assault on her clitoris and invasion of her vagina with his tongue. It didn't take long before her lubricating juices began to flow on their own and the German Shepherd eagerly explored her pussy, seeking them out. He relentlessly lapped them up.

Despite all the pleasure she felt, she knew she couldn't let him go any further, at least at the intellectual, civilized level. In her mind, she formulated a plan for escape. She would twist around and get up, then make a run for it. Even if she didn't make it back to her house, almost anything was better than getting raped by a dog. Maybe, she thought, she could find a tree branch or big stone to use as a weapon to scare him off with.

Elen made her move. She twisted around and got onto her hands and knees. Just before she was able to get fully to her feet, she felt his powerful forepaws wrap around her slim waist. His weight was like an anchor and she sunk back to her hands and knees with him on top. His rough paws scratched her sensitive sides, and his coarse stomach hair brushed against her back. She struggled valiantly for a minute, but there was no way she, a 110-pound girl, could get him, a 190-pound dog, off of her.

"Great escape, Elen. Way to go," she thought to herself. "What's he going to do now?"

That's when she felt the tip of his cock touch her bare thigh. She hadn't realized that he would try to actually penetrate her. She didn't think such a thing was even possible between a dog and a human, but here she was. Elen looked down between her hands and knees and saw it. It was huge. It was at least nine inches long, bright red, and glistening wetly.

"Oh fuck! I can't let this happen to me!" She struggled with all her might, but all it served to do is exhaust her. Once she finished struggling, the victorious dog began to try to find her pussy. Elen's pussy was wet and open from her previous stimulation. It was ready, even if she was not. He was used to the height a pussy was on a bitch, not a human, so he kept jabbing and missing. Each jab he went a little higher, until finally he hit what he was searching for, Elen's pussy. Elen let out a cry of despair, finally resigning herself to what was about to happen. After entering her, the German Shepherd made a quick series of thrusts, which pushed his entire cock deep into her. His cock now fully inside her, Elen could feel the tip of his cock pushing against her cervix. At first the stretching of her pussy hurt a lot, but before long it subsided. She had to admit, this felt totally unlike her experience with John. This dog's cock felt hot inside her. Strangely enough, that heat felt very erotic, and only heightened her pleasure. This dog was almost much larger than John, filling her fully and completely.

Finally comfortable and situated, the dog began to hump her at a rapid pace. In and out. In and out. Every time he pushed fully into her, the tip of his cock would press against her cervix, and the fur at the base of his cock would brush against her clit, which by this time was engorged in arousal. Her mid-sized tits jiggled back and forth with every hump, and her nipples hardened. The pleasure rapidly built within her. Before long she couldn't help herself, and she began to hump back at him. Feeling something wet hit her neck, Elen looked up at him. His tongue was hanging out of his mouth and was dripping his saliva all over her hair and neck. At this point, Elen was so horny so as to be past all reason and morals. She opened her mouth and let some of his saliva drop into it. Surprisingly, it tasted good to her. The thought of performing such a taboo act hit her then, and pushed her over the edge into oblivion. She orgasmed. Hard. She screamed out in bliss for what seamed like forever. The sounds of her screams were muffled by the old-growth trees surrounding the field. No one would be hearing them. The orgasm seemingly made every muscle in her body fire spasmodically, and still the dog continued to hump. Seconds after the orgasm subsided, she felt a pressure developing at the base of his penis, just outside of her pussy-- his knot.

A sudden fear of being torn apart by it seized Elen. She took hold of the base of his cock to prevent it from entering her. It felt hard, hot, and a slightly slimy. It continued to grow until it was almost as big as a baseball. Then his frantic pace slowed to a stop. Thinking it was over, she let go of his cock. Suddenly, he pushed forward with tremendous force, almost knocking her face into the ground. The huge knot pushed itself half way into her. Before she could stop him, he humped again and it was pushed the rest of the way into her vagina, where it lodged itself. Her pussy hurt, as it was stretched to unbelievable proportions to allow the knot to enter.
The huge dog humped a couple more times, softly, then stopped and seemed to tense up. He howled, and she felt his cock begin to spew cum deep into her womb. His cum was even hotter than his cock and it boiled deliciously into her. He continued to spurt cum into her for what seemed like forever. Elen felt their combined juices running down her leg. Finally it stopped. The huge dog let out a contented sigh, and licked her neck affectionately. After a beat, he tried to pull out of her, but his knot held him it, and it caused her some pain.