S1·E14 The Thin White Line

Frank enters a hospital emergency room looking for Catherine, who is working the night shift in child counseling. Suddenly, paramedics rush in with a bloodied woman on a gurney. Frank is inexplicably drawn to the stranger, and as he moves closer, notices a curved slash on her palm. He raises his own right hand, revealing a thin white scar which matches exactly the slash on the victim's hand. The woman dies from her injuries.