Watch Unsolved Mysteries: Behind the Legacy for Free: How to Stream the Movie Online at 123Movies. . Sitting down with co-creators Terry Dunn Meurer and John Cosgrove, along with long-time actors, producers, and directors of the show, this documentary special pulls back the curtain with behind-the-scenes stories from research and casting to solving mysteries soon after episodes aired. With never-before-seen outtakes of beloved host Robert Stack and a look into some fan-favorite moments. This program honors one of television's most enduring and recognizable shows as well as the fans who were integral to its success.