Ella Knox arrives home and calls out for her mother. Strangely, nobody responds, leaving her excited about having the whole house to herself. But her excitement doesn't last long as she hears a voice from the living area.
Heading there, she encounters
Penny Pax looking incredibly attractive in a stylish blue outfit. Inquiring about her presence, Ella learns that Penny is an acquaintance of her mother. Oblivious to the unplanned visit, Penny explains that she has been friends with Ella's mom for a long time and visited to escape her mundane routine.
Seeking to study for her biology exam, Ella excuses herself, and Penny, who happens to work in the biology department, offers to assist her. Grateful for the help, Ella invites Penny up to her bedroom, unaware that her stepmother,
Reagan Foxx, coached Penny on what to say. As Penny starts to seduce Ella, it becomes evident that the only biology she is focused on is Ella's physique.
Reagan comes home and hears sounds from upstairs. Upon discovering the girls engaging in intimate activities, she bursts into the room demanding an explanation. Revealing Penny as her lover, Reagan confuses Ella, who is uneasy about having been involved romantically with her stepmother's partner.
However, Penny reassures Ella and convinces Reagan that it's not a serious issue as they have had separate partners before. Proposing a reconciliation through a biological exploration of Ella's anatomy, both girls slowly warm up to the proposal. By the end, it seems Ella is in for a remarkable grading experience.