Synopsis

A series of three murders in Austin, Texas, each eerily similar, prompted investigators to consider the possibility of a serial killer. Yet, the perpetrator left behind no trace – no forensic evidence, no DNA. The police launched a desperate investigation, the search for leads intensifying until a man testing a new thermal imaging scope captured the movements of an unknown individual on the night of the first killing. As "48 Hours" correspondent Maureen Maher reports, this unexpected evidence pr