Rosalyn Sphinx has a rare disorder that causes her to have uncontrollable orgasms that she can't stop from coming. Living with her stepbrother Lucas Frost is a challenge, since each time Rosalyn cums in front of him Lucas gets aroused. Lucas's dad, Dick Chibbles, sees Lucas looking at his stepsister with bedroom eyes one day in the living room and kicks Lucas out lest Rosalyn get the idea into her head that fucking might cure her problem. When Dick dozes off in front of the TV, though, Lucas sneaks back into the living room to be gratified with Rosalyn making the exact moves Dick feared she might.

They start in the living room, with Rosalyn sdeep throating Lucas's fuck stick until he's nice and hard. Dick is still sleeping, so Rosalyn takes the risk of peeling off her shorts and climbing aboard Lucas's hardon right on the couch to ride him. Her body loves the way Lucas fills her right up, but Dick is too close for comfort. Leaving their discarded clothes on the floor, the stepsiblings relocate to the bedroom, where Rosalyn lays down on the bed and welcomes Lucas back inside.

Fucking his super skinny stepsis is everything Lucas has dreamed of. When she turns over onto her hands and knees, he enjoys the opportunity to shape that ass with his big hands while banging her from behind. He has just pulled out to cum all over Rosalyn's ass when Dick bursts into the room. After waking up from his nap, he spied the clothes on the floor and knew exactly what his deviant kids were up to.