As RIPA is sent to explore the raised up new drift, the crew makes a surprising discovery: Another bulkhead. At the end of last season, these old bulkheads surrounded extremely high-grade ore. Will this bulkhead prove just as profitable? Patrick urges caution, however, as the bulkhead itself is surrounded by unusually high readings. Undeterred, Eddie makes the decision to tear down the bulkhead. In order to do so, the crew will need to stabilize the raise to make it safe to work up there.
At the Octave Mine in Arizona, Kristen begins her investigation by checking out the ruins of the area. Once a prosperous boom town, the Octave fell into disrepair around the start of World War II. Kristen meets with the Octave Mine's operations manager, Gary, to learn more about the strange occurrences within the mine that have sent two mining crews packing. He informs her that the crews mostly saw shadows and heard strange knocking sounds, not unlike what the crew at the Crescent has been experiencing. He also tells her about Charles "Bloody" Stanton, an outlaw who tried to take over the town back in the day, leaving a trail of death and destruction in his wake.
At the Crescent, the crew prepares to break down the bulkhead. Despite some unusually high readings, Eddie orders Dingus to axe down the wooden barrier. Behind it, they find an empty room; some quick assaying on the spot reveals some good high-grade ore. Patrick finds a small hole with a strong airflow beyond it; Eddie makes the call to blast through to chase the ore.
Patrick performs one quick reading with a Piezoelectric microphone that converts vibrations into an electric signal that can be picked up with a voice recorder. He places the microphone on the ceiling of the newly unearthed room for a few moments to collect his audio sample, then heads out as the crew prepares their blasting work.
As she investigates an unsettling nearby cemetery with its stone rubble gravesites, she begins to get unexplainable high EMF readings when nothing could be giving off such a high frequency. While conducting an EVP session, one of the many white wooden crosses tumbles over without explanation; she's unsure whether or not to attribute to the strong wind or something paranormal.
She heads off to meet with the Octave's security guard to learn more about the legend of the Blue Devil of Octave. She's surprised to find out that he refuses to go into the mine because of it, believing that the Blue Devil guards the gold. Stan, meanwhile, meets with the mine owner to see if the Octave is worth his crew's time. With solid mining data and plenty of sparkly gold ore recently mined from the Octave, Stan sees a prosperous opportunity for him and his men. Before he can seal the deal, he wants to check out the mine's paranormal possibilities and offers to help Kristen conduct a paranormal sweep of the mine.
As Stan and Kristen enter the Octave, they begin to experience EMF spikes right away. They begin seeing some shadows and hearing strange noises. Kristen captures an unusual shadow on an IR photo; she and Stan head after it. As they venture deeper, Stan notices some very promising quartz veins. They check out the drawing that could possibly represent the Blue Devil; as they investigate, they hear a loud breath near them, as well as some knocks. They start an EVP session.
Their readings begin to spike and they both see a dark shadow dart away at the back of the mine. As they follow it, they see the shadow dart down a deep hole into the earth. As the readings return to normal, they leave the mine. Stan is practically speechless about what they encountered first-hand in the Octave. Still, he feels confident that the Octave will be a profitable investment of his crew's time and energy, despite the strange occurrences. After all, it's nothing his men aren't used to at this point!
Back at the Crescent, a freak summer snowstorm forces the crew off the mountain. When it's safe to return, Patrick shares some more evidence about how their mining efforts are creating more paranormal activity within the mine. His Piezoelectric microphone reveals a disturbing growl that seems to be emanating from the very rock itself. Eddie, ever the skeptic, remains undeterred, sending in Jay and Dingus to blast through hole with the strong airflow.
As Jay and Dingus finally break through in the new drift, they come across something they hadn't expected to find at all.
Kristen sees the opening in the side of the mountain for herself and makes a startling realization about the way the mine aligns with Baker City.
In this shocking season finale, the miners finally approach the mother lode as Patrick and Kristen reveal the final shocking pieces of the paranormal puzzle.
Stan and Eddie check in with mine owner Larry to outline their prospects for what little remains of the mining season.