Mackenzie Moss just got done watching a thriller movie and now she's terrified to shower alone in their vacation home. She asks her stepbrother, Seth Gamble, to guard her without peeking. Seth decides it'll be funny to prank Mackenzie, so when she gets into the shower he runs to the kitchen and grabs a knife to pretend to replicate the movie's penultimate scene. Mackenzie runs off to her room to cry. Seth feels badly, so he decides to apologize. Mackenzie asks why Seth is being such an ass since she thought he liked her.
Seth tries to apologize again, putting his hand on Mackenzie's thigh. She calls him on it, but when he removes his hand she puts it right back, but higher. He takes the hint, fingering his sister beneath the towel. In return, Mackenzie tugs Seth's pants off so she can wrap her lips around his hardon. Sucking him off, she deep throats Seth's cock until she can't wait another moment to climb on top and start riding him.
Mackenzie is so tiny that Seth finds he can do all kinds of acrobatics with his stepsister. He lifts her to set the pace as she rides him, then dominates her from above when she falls backwards onto the bed. Getting onto her hands and knees, Mackenzie invites Seth to give her a doggy style pussy pounding. As he fucks her, she begs him to cum inside. He obliges, glutting her with a creampie that drips down onto the bed when he pulls out.