A team of Americans explores a mountain in the Philippines to search for a treasure rumored to have been buried by Gen. Tomoyuki Yamashita in the closing months of World War II.
Digging continues at Breach-6, but when the team unearths a possible water trap the excavation is put on hold; the team conducts a LiDAR scan that reveals a cave, perhaps used by Japanese soldiers during the war.
After discovering a bomb marker, the team brings in an explosives expert to search a cave that may have been a headquarters of Gen. Yamashita during the war; a potential booby trap and the first hint of treasure.
The team triggers a possible water trap in the cave and is forced to stop digging; Martin Flagg believes the Story Rock indicates a tunnel behind a waterfall, and the team brings in a diver to explore the plunge pools for an entrance.
Unable to find a tunnel at the waterfall, the team is guided by an animal marker to a boulder carved in the shape of a turtle, which leads them to a golden lily symbol indicating a secret backdoor entrance.
The team attempts to prove if a tunnel exists behind a unique formation of rocks they believe is a secret backdoor entrance into the mountain.
As the team zeroes in on a tunnel that may be part of the treasure labyrinth, Bingo learns that part of dictator Ferdinand Marcos' fortune may have been stolen from Yamashita's treasure and uncovers a possible link to a CIA conspiracy.
Peter meets with a man who warns of the deathly risks in searching for Yamashita's treasure; the team clears the last obstacles and finds a secret tunnel directly into the mountain.
An advanced satellite scan of the mountain reveals metal deposits underground; the team targets three sites believed to be the access points to Yamashita's gold: a waterfall, a crater known as Breach 6, and a camouflaged tunnel.
With new evidence suggesting the location of a possible treasure vault beneath the waterfall, John is determined to find a way in, but Mother Nature is wreaking havoc on his plans; information is revealed about the knife that was found.
Another promising clue at Breach 6 leads Rick to believe they're on the right track; John hits a roadblock on his search for a tunnel entrance near the waterfall, Bingo makes an incredible discovery that could lead him to Golden Lily treasure maps.
John plans to drill across the mountain; Rick finds an artifact at Breach 6 that could confirm Japanese military presence; Levi and Geo make a grim discovery in the tunnel; Bingo meets someone with rare and valuable knowledge.
Breach 6 reveals its first piece of treasure; Levi and Geo come up with a creative solution to get past a mysterious collapse in the tunnel; while drilling toward a possible treasure vault, John and Rob make a startling discovery.
As the team finally gets to the bottom of Breach 6, startling new evidence suggests they might be too late; the miners trigger a hazard in the tunnel, which threatens their safety; Bingo unearths alarming evidence a little too close to home.
When a dead end in the tunnel threatens to close the door on exploration, a back door opens. Using their recently decoded Golden Lily map, the team discovers new access points, hoping to get under the waterfall by any means necessary.
In the season finale, the team finally reaches the void space under the waterfall, giving them a glimpse of what lies inside. But excitement is short lived when unexpected visitors get in the way. Meanwhile, the team investigates leads for other possible Yamashita treasure sites throughout the Philippines, uncovering evidence that any one of their 25 new treasure maps could lead them to the Lost Gold of WWII.
