Billy Jensen is the acclaimed true crime investigative journalist, who helped finish Michele McNamara's haunting book, "I'll Be Gone in the Dark," after her death. The haunting story tells the tale of The Golden State Killer, a serial killer who terrorized Californians. Just months after its release, police announced they had a suspect in the case. Jensen talks to me about this extraordinary story, the process of writing the book, and his path to becoming a journalist specializing in unsolved crimes.