After her father remarries, the stepmother moves into the household, but she is only home four days a week. One day, the son secretly witnesses his father and stepmother engaging in an illicit affair. He soon discovers that the stepmother never actually divorced her previous husband. Armed with this secret, the son blackmails her. Yielding to his threats, she is forced to masturbate using sex toys and ultimately ends up being coerced into having sex against her will.