Det. Richard Gagnon fills his days with thoughts of the dead. Their names, faces and murders are always with him. Gagnon, a homicide detective in Seattle, WA., works Cold Cases – cases shelved and forgotten that no one has been able to solve. These... (more) are cases with physical evidence, sealed and literally frozen in time, for 10, 20, sometimes 30 years. "My god, it's a murder, and someone is out walking the street who's a murderer, and you have to take this guy down," says Gagnon. "We often will read a case file in a cold case again and again. It's more than just a name. It's a person," says Det. Greg Mixsell, who is Gagnon's partner. Together, they make up Seattle's entire Cold Case Squad. In Seattle, there are more than 300 unsolved murders. Yet in the last three years, the Cold Case Squad has cracked almost 20 of them, a remarkable record. But now, the squad faces their greatest challenge yet, as they try to solve two of this city's most notorious killings -- beginning with the murder of Mia Zapata. It's a case that's been cold for more than a decade. Correspondent Harold Dow reports.