Skipp Porteous has been a minister, a First Amendment activist, a convert to Judaism, and a mole hired by the FBI to infiltrate neo-Nazi groups. But it’s his work over the past few years as a private investigator that led him to the famously unsolved case of a man known only by the alias “D.B. Cooper,” who hijacked an airplane in 1971 and left it, midair, via the aft stairway with parachutes and $200,000 ransom, never to be seen or heard from again. As Porteous recounts in his new book Into the Blast: The True Story of D.B. Cooper, he was contacted nearly four decades after the Cooper incident by a man who had come to believe that his brother was the hijacker. After a two-year investigation, Porteous is inclined to agree. Reporter Jon Kalish spoke to this unusual private eye.