Let him drive...

Beth couldn't suppress little moans of pleasure while Seth worked her nipples with his tongue and teeth, gripping firmly into the flesh of her ass and grinding her crotch against his erection. If this was what it was going to take to get what she needed from him... Beth bit her lip. I'm...not exactly...hating it, either.
"I've been looking forward to this..." Seth breathed into her cleavage. "...ever since you started. I always knew..." he turned his face up towards hers with a predatory grin. "I'd have you one day."
"Seth..you don't..." Beth had to catch her breath. She was shaking with adrenaline and arousal. "I just need..."
"Don't worry...I know what you need."
With that, Seth pushed her off his lap and onto her feet, standing up with enough **** to send his chair rolling to the back wall. Without a word, he spun Beth around and pushed her over his desk. Beth's tits squashed against the cool surface, and she shuddered as Seth ran his hands down her back, squeezing her ass. Then, she heard the tell-tale fumbling of his belt and zipper. Oh..oh no...I can't...
"Seth! I...."
"Shhh.....you want my help, right? Besides...." his hands spread her legs at the knee, running up her inner thighs as she bit down on a gasp. His fingers cupped her crotch, and he chuckled. "...it seems like you want more than my help." She could feel her wetness, moistening his fingers even through her panties. She stopped fighting a low moan, letting it out.

"...j-just...remember...the deal...."
"Don't worry...I won't forget anything..."

Within seconds, Beth was gripping the edge of the desk, moaning loudly with each thrust as Seth fucked her from behind. A part of her brain hoped that Sun was long gone. A smaller part of her brain was filled with guilt and shame at her actions, but the vast majority held nothing but illicit pleasure. Seth's dick was perfectly molded for her pussy, it seemed to her. Not too big or too small, and his technique had her eyes rolling up as he slowly but surely increased the intensity.
"You've been looking for an excuse for a long time, haven't you Beth?" His tone was teasing, almost cruel. Beth wished she could deny the words, but she didn't have the brain power necessary at that moment to form coherent sentences.
Beth couldn't have said how long the sordid little indiscretion lasted, but before too long, Seth was breathing hard, and then he pulled from the desk, pushing her onto her knees.
"Take it, baby." Seth was sttroking furiously, and faced with the choice of taking his load on her face or down her throat, Beth opened wide to engulf his cock just before he shot his load.

Once he stopped spurting, Seth sat back onto his chair, leaving Beth spluttering and coughing on her knees.
"Not bad...we'll have to take our time next time."
"Next time!?" Beth was somewhere between fury and incredulity.
"Relax...I'll get your shift covered, and any more you need for the next few weeks...I'm just saying..." he leaned forward to stroke her cheek and grip her under her chin. "You'll be back for more."
Beth didn't know what to make of Seth's domineering arrogance. She wanted to defy his expectations, but the truth was...she was intrigued by his new energy. She hadn't cum, but she got the sneaking suspicion that he had not wanted her to... that he had intended to leave her wanting more.
"Just...just remember our deal, ok?"
"Of course. I'll see you around." He was already buckling his belt and zipping up his trousers. "Have a good night."
Beth stumbled out of the office a few minutes later, still not quite believing what had happened. He's going to make it happen for you. That's all. An exchange of services. Her rationalizations felt a little hollow in her own head as she started the car and headed home.