A forceful woman despises her timid, serious adult stepsister, whose innocent appearance makes everyone think she is dependable. Whenever the stepsister tries to act superior, she is slapped, sexually dominated by another woman, and reduced to total obedience. The torment expands into forced swapping involving both women’s boyfriends. The timid couple begins in tears and confusion, but wave after wave of pleasure gradually strips away their restraint and reveals their growing lust, leaving the aggressor with a new pair of toys she will not tire of soon.