Duane Ollinger believes there's a fortune of gold buried beneath his property in Utah. He's not going to stop until he finds the treasure, no matter the cost.

With an access tunnel to an underground cavern finally opened and a tantalising clue discovered, Duane's son Chad takes a risky dive into the flooded cave system.

Duane and the team search for new access points to the underground cavern system. But something lurking in the darkness forces everyone to re-evaluate their safety.

The team discovers mysterious ancient markings on a cliffside, and a mining shaft dug deep into the mountain that could lead them right to the gold.

Duane employs ground-penetrating radar to scan the land, leading to a mysterious finding. Trespassers prompt Charlie to increase security on the ranch.

As winter closes in and the digging season nears its end, Duane takes a final shot at getting into the underground cavern and uncovers a whole new mystery about the land.

The crew return to the ranch to strategize a new plan to get the box out of the underwater cave. And, Charlie investigates a mysterious death on the ranch.

When a windstorm ruins visibility in the water, Chad considers a risky blind dive to extract the box. Plus, intruders are discovered on the ranch.

Chad makes a huge mistake that could prove costly. Plus, a shocking discovery inside the box forces Duane to rethink everything.

Determined to get into the cavern, Duane explores new methods to find a dry entrance. Meanwhile, Chad takes to the skies in search of a natural opening.

After Duane makes a costly mistake, Eric and Chad finally discover what they've been looking for. However, the crew gets distracted by mysterious intruders.

After the crew drills into a dry cavern, they must devise a plan to protect themselves from poisonous gases. But trespassers threaten their progress.

As the crew explore the cavern, they are overcome by a deadly and invisible gas cloud. It'll take a complicated rescue mission to get them out alive.

Duane and Chad Ollinger return to the Ranch to unearth $3 billion in hidden treasure. Claim jumpers invade the property, threatening to derail everything.

When an underground tsunami floods the cavern system, Duane and his team enter it from higher ground - discovering evidence of Aztec artifacts.

After uncovering a bar of gold at the Bead Site, Chad and James set out to research where it might have come from and see if they can find more.

The team tries a dangerous manoeuvre on the trail of the Lost Rhoades Mine to access the Mormon Eye cave. Duane finds more poacher sites on the ranch.

The team resumes drilling into the Energy Zone. Duane takes a stand against the poachers. Charlie finds a dead animal with unusual bite marks on it.

While drilling into the cavern for Aztec gold, the team strikes an impenetrable object deep underground that reveals the truth about the Energy Zone.

After hitting a meteorite deep underground the team searches for an alternate route into the cavern. Chad discovers a clue that leads to a breakthrough.

The results from the radiocarbon testing are in, which will tell Duane if the box is Aztec or not. And, the men discover they are being watched by a high-tech camera.

Searching for the hidden entrance to the cave system, the team finds an ancient vent shaft above the Energy Zone but are thrown off by an explosion.