Twins Regina and Renata are so identical that even their mother can't tell them apart. Tragedy strikes when one of the twins is viciously murdered. The remaining twin is so traumatized, she reverts to the cryptic language she once shared with her sister. What's more, since identical twins share identical DNA, there is no way to tell which girl was the victim. The parents believe the surviving twin is Renata and have no choice but to commit her to an institution. There she lives, incomprehensible to the rest of the world. Until the day Mark, a family friend, comes to visit and then the young girl utters her first intelligible word. Brilliant and beautiful, Renata gradually reacclimates herself to the outside world. But she is far from recovered. Her nightmares grow steadily more frightful, followed by wild fits of hysteria and dark mood swings. Meanwhile, as Seattle is plagued by a grisly serial killer, Mark has a terrifying realization: The murders coincide with Renata's strange outburst. Could she be the killer?