Rob Nelson investigates rumors of a secret underground escape route used by the infamous gangster Al Capone. In Washington state, Rob tries to uncover who -- or what -- built a vast landscape of earthen mounds in Washington state.

Rob Nelson explores mysterious tunnels beneath Denver's airport and capitol building to investigate rumors of a secret organization operating below. In Ohio, he tries to uncover the ancient secrets of a mound shaped like a serpent.

Rob Nelson hunts for a legendary mass grave that could expose a dark secret of America's industrial past. High in the mountains, a giant lake is mysteriously disappearing, and Rob uses cutting-edge technology to find out why.

Rob Nelson examines a set of bizarre markings that suggest a violent clash between prehistoric beasts. In California, he investigates if a strange lake is a home to alien life.

Rob descends into a cave 30 feet beneath Texas in search of evidence of a mass extinction event. Then, he heads to Lake Michigan to investigate a Bermuda Triangle-like phenomenon that has caused ships to vanish for centuries.