Cruel Intentions(1999)
 

Kathryn and Sebastian, two wealthy, manipulative teenage step-siblings from Manhattan's upper-crust, conspire in Cruel Intentions, a wickedly entertaining tale of seduction and betrayal. The stakes are high when the duo agrees upon a deliciously diabolical wager of sexual conquest without consequences. The pawns? The naive Celcile Caldwell and the virginal Annette Hargrove.