When Freddy and Juan get an SOS from an Oregon couple's mine, they must unravel an underground mystery buried beneath a dried riverbed. Facing misleading dredge tailings and a faulty homemade wash plant, the guys call in all-new tech as a final hope.

Two rookie miners in MT desperately need to double their gold after a disastrous start to the season. Battling a personal crisis, Juan rejoins Freddy as they follow signs of old mining tunnels and use new technology to uncover ancient river channel gold.