Trapped To Breed

I have a massive kink for the idea of my wife's best friend trapping me in her home and using me for sex. She has an attractive face but is fat and lonely. I like think about me going around her house to do a small job my wife has agreed I'd do for her friend. But then she drgus me. I wake up tied to her bed, she's dressed in sexy lingerie and stockings and has fed me vigra. She tells me I can't leave until she's impregnated. She's ovulating right now and takes charge straight away climbing on top and riding my cock countless times until I fill her with my cum. She tells me it's our little secret and she'll tell my wife the kid is from a one night stand.