After a turbulent childhood, identical twins Adeline and Alyssa Collins have finally settled into life with their father, stepmother, and stepbrother. As they begin their senior year of high school, both are Ivy League-bound and have an unbreakable bond. But when their stepbrother is found dead in the family's basement and one of the twins' DNA appears at the crime scene, they begin to question whether they really know the people around them- or themselves.