A dirty picture of Gretchen's sister and father

"You want me to recreate the worst thing I've ever made a student do?" Professor Klein asked coyly.

Anxiety shot through Gretchen's body. Or was it horniness? She didn't care. She could do it. She wanted to be among those who lusted all the time. "I want to go farther." Gretchen didn't know how she could be more clear, or more honest, even though she couldn't possibly predict what was happening in Professor Klein's clever mind.

"You have a sister?" Professor Klein asked.

Gretchen nodded, understanding. 'She wants me to deliver Erin to her' she thought. That wouldn't be too hard. Erin wasn't like Gretchen. She was a normal girl, not overly sexual, but not opposed to sex. At least, so Gretchen thought. They'd never really talked about it. Gretchen had always refused to, and refused to give sisterly advice. "I think you should just forget about men and sex" She'd say whenever Erin came to her with a problem. But Erin didn't. She definitely wasn't a virgin. She might even be relatively agreeable to all this.

"And your father?" Professor Klein went on.

That question seemed more dubious. 'Why would she be asking about dad?' Gretchen wondered. But still answered, "He's a state Congressman"

"Great!" Professor Klein had clearly made up her mind. Though Gretchen didn't exactly understand how or with what. "You have one week to return to me with a picture of your little sister sucking your dad's cock."

And Gretchen didn't react. But that image immediately ran through her head. Erin's soft young lips sliding up and down Dad's hard member, bobbing over and over, transformed into an incestuous freak, never to turn back.

The image lingered in Gretchen's mind all day as she eventually returned home. And all night too. She rubbed herself off to the thought of little Erin saying "Oh god Daddy, your cock is so delicious." At first it worried her that the idea turned her on as much, but she reminded herself that this was the type of person she was now. She was one of Professor Klein's horny products. And she wasn't sure if she just wanted to fantasize about it or actually make it happen. But she knew she couldn't. It would never happen. It could never happen. There was nothing she could do in a week's time to convince Erin or Dad to do such a thing.

The next morning, Gretchen awoke with her hand already down her panties. She took a quick shower, masturbating again. This time thinking of her Dad holding the top of Erin's head as he said "Yes darling, suck your daddy's cock!"

Then she did something she thought she'd never do. She shaved. Completely. She shaved her pussy smooth. 'This is the type of person I am now.' she said to herself again.

Gretchen headed over to Daddy's place that afternoon. It was Saturday and she knew Erin would be off school and hanging out at home with their father. She wasn't sure what she was going to do or why. She knew she'd never accomplish the task that Professor Klein had given her. But still she wanted to see Erin and Dad.

When she walked int the door Erin was in the kitchen, propped up, sitting on a coutner-top, munching a carrot and staring at a TV.

Gretchen smiled "Hi hon!" she said, giving her kid sister a poke in the side. She wondered if it would be obvious that she was a changed person.

Erin wore a pair of short shorts that exposed her long shapely legs, and a lettered jacket from high school. She was a runner and it showed in her petite, tight body. Her hair was the same chestnut color as Gretchen's but curly. And people could often easily tell in their faces that the two girls were sisters.

"Where's Daddy?" Gretchen asked, as usual.

"Workin on Saturday again," Erin crunched her carrot.

It was difficult for Gretchen to watch Erin's mouth wrap around her carrot without picturing it as a cock. In fact, she was having all kinds of inappropriate thoughts about her sister for the first time.

How many dicks had Erin ever sucked? Did she swallow?

What did she look like naked? Were her nipples small like her own or big? Was she shaved?

Did she talk dirty? Did she give messy blow jobs? What would she do right now if Gretchen grabbed that carrot out of her hand, bent her over and sodomized her with it calling her "my little whore sister."

Gretchen took a deep breath. Her crotch was starting to get wet. And suddenly she knew something.

She'd never be able to stop thinking about this. As impossible a task as it seemed to get her sister to suck her dad, she had to. It was the only way to clear it from her mind. A+ or no A+, dissappointed professor or not. She had to do this for her own sanity. But how?

There was only really one option. She'd have to seduce Erin first and the two of them could work together on Daddy. It would be difficult for any man to resist two pretty girls begging for his dick. Even if they were his daughters. Although even that wouldn't exactly be easy. As a girl who'd avoided sex for most of her life, Gretchen didn't really know how to seduce someone.

Erin finished her carrot and flung her curly brown hair from her face. "I'm free all day Gretch, wanna do something?"