The New Girlfriend (1999)

In Australia, the executive Kate sees a young woman undressing her stolen dress in the swimming pool of a club, and regardless of the contrary opinion of her mate Phil, she decides to steal it back. Later her teenager son Matt is approached by the smalltime thief Rachel, the woman who stole the dress, and after spending some leisure time with her, they go to his middle class house. Soon, Rachel's friend Nick joins them, and Nick ties Matt to his mother's bed while Rachel masturbates him and cleans him with his mother's dress. The abused boy has a trauma, and his mother seeks revenge against Rachel, who returns with her friends, in escalating forms of retaliation until a tragic conclusion.