Sterek AU: Derek’s ex-girlfriend came back to Beacon Hills and met Derek in the bar. A lot of things changed since she left months ago. Including Derek. He was even hotter now than last summer (Who knew it’s possible). So she couldn’t resist. Uncontrolled desire. Desire for his lips, his arms and hands, his eyes, his every muscle, his everything. She came closer and then pounced onto him without a word but with her tongue and lips. Derek hardly recognised her and tried to push away but she grabbed him like lion a gazelle. Not funny at all ‘cause at the same time Stiles walked into the bar to meet Derek here and to go grab some curly fries. 
“Hhhm… Derek! What’s going on?" 
Finally she got off of her prey when realised they’re not alone anymore. Derek felt relieved.
"Stiles. I’m sorry. It’s Catherine. Remember I tol-”
“Ohhh, yes”, Stiles nodded. “How couldn’t I”. He turned around and walked away fast.