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, capitol building, and downtown to investigate rumors of a secret organization that operates below. In Ohio, he tries to uncover the ancient secrets of a giant mound shaped like a serpent.

What caused the deaths of 57 Irish railroad workers in 1832 Pennsylvania at a place called Duffy's Cut. And then, we look at Mountain Lake in Virginia that has mysteriously lost most of it's water.

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 Nelson 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 an unexplained, Bermuda Triangle-like phenomenon that has caused ships to disappear for centuries.

Rob Nelson heads to California to investigate a network for major fault lines that could set off an unprecedented mega-quake. Then, he explores a mysterious sinkhole that some believe is an endless pit to the center of the Earth.

Rob Nelson investigates investigates a cluster of ancient ruins in New England that suggest Europeans arrived in the Americas almost 1,000 years before Columbus. Then, he heads to California where a dormant super volcano may be showing new signs of life.

Rob Nelson investigates the mysterious pattern of rocks at the bottom of Lake Michigan known as Underwater Stonehenge. At the notorious Alcatraz prison, Rob uses state-of-the-art technology in search of rumored escape tunnels.