In the throes of teenage hormones, a curious stepsister can't help but sneak glances at her stepbrother's growing bulge. One day, she catches him masturbating and, intrigued, offers to help. She tentatively takes his throbbing cock in her petite hand, then her mouth, learning the art of giving head. Her brother, overcome with lust, guides her head, teaching her how to pleasure him. As she gains confidence, she takes him deeper, gagging slightly but eager to please.