AllMovie

My Stepdaughter follows Jill (Emmanuelle Vaugier, “Mistresses”), a recently remarried woman trying to connect with her teenage stepdaughter Casey (Niki Koss, “Girl on the Edge”) while raising her own young daughter, Lydia (Ava Acres). Secretive, with a penchant for dark clothes and black make-up, Casey tries her best to create a rift between her dad and Jill. When Jill’s mother suddenly and mysteriously dies, she suspects Casey is somehow involved. As Jill puts the puzzle pieces of her mother’s death together, a deadly battle for control ensues between mother and stepdaughter with Lydia’s life hanging in the balance.