Disaster strikes when Duane and Charlie attempt to drill down a smoke vent at the Bead Site. Chad and Josh follow the fault line back to the collapsed mine. Eric explores an indigenous site in Ohio that holds clues to Blind Frog Ranch.

A hidden cave entrance below a lake could finally lead the team into the Keyhole Chamber. After training in Florida with some of the best cave divers in the world, Chad navigates a deadly maze of flooded tunnels and makes a shocking discovery.