After the investigators review the latest round of paranormal evidence throughout the town of Sumpter with the miners and their families, everyone is back on the mountain to get their payload. But the next morning presents a potentially deadly obstacle: A massive forest fire on the mountain threatens to overtake their mining camp. With little time for debate, Stan orders everyone off the mountain until the coast is clear.
The downtime off the mountain might be a nice break for the miners as they spend time with their families in town, but every minute not on the mountain is money down the drain. Kristen and Patrick decide to take the opportunity to investigate a lead about the Chinese miners, one that takes them a few days away from camp. They discuss their concerns with Stan about leaving the miners alone with no backup should anything paranormal occur at the mine or in town; Stan assures them they'll be fine.
Kristen and Patrick head down to Hell's Canyon along the Snake River, the site of the brutal massacre of three dozen Chinese miners, whose bodies were callously dumped in the river by local horse thieves.
Back at camp, Stan learns the fire has been contained and that it's safe to go back on the mountain. Despite the fact that the investigators won't return for a couple of days, the crew makes the decision to head back to the mine as soon as possible to make up for lost time, including pulling double shifts.
Bucket and Jay start the day shift by setting up a ventilation system as the crew heads deeper into the mountain. As they get started, their brand-new generator cuts out unexpectedly, with no explanation. Worse still, it won't restart. Greybeard and Duck head deep into the mine to assay the rock they've revealed thus far. Duck swears he can hear other miners working in the shaft, despite the fact they're the only two in there. At first, Greybeard doesn't hear anything, but as Duck gets more and more worked up, he too begins to hear the sound of hammers against rock. Sensing the noise is paranormal in nature, they leave the mine.
Eddie, Mikey, Jamol and Dingus take over for the night shift, already playing catch-up from the day shift's mishaps with the generator. Back at the camp, Stan, Greybeard and Duck lose power in their shacks.
After several hours of travel by car and boat, Kristen and Patrick arrive at Hell's Canyon. They set up their base camp in the wilderness with their boat captain set to return the next morning. For all intents and purposes, they are completely alone for their night investigation. As they do a baseline sweep, both their EMF and K2 detectors start spiking wildly, when there shouldn't be any kind of electrical signal at all outdoors.
They take the opportunity to begin an EVP session just footsteps from their base camp. Patrick's translator colleague has given him a list of standard EVP questions translated into Cantonese so he can try and make more accurate contact during their investigations. Before long, they hear noises not too far from them in response to their questions backed up with equipment spikes. Kristen and Patrick try to chase down what sounds like another person creeping around their camp. Their chase takes them right to the water's edge.
Just as it seems activity has died down, they hear a distinct "Hey!" calling for their attention, sending them off in another direction, with more noises and EMF spikes. Their hunt takes them to a rocky ridge; both Kristen and Patrick think they see someone moving at the top. Despite the steepness and potentially loose rock face, Patrick free climbs the ridge to see what's up there. After nearly falling off the ledge, Patrick makes it to the top - but finds nothing there. He carefully makes his way back down and they decide to head back to their base camp for the night.
Back at the mine, the night shift has been hit with a number of setbacks including a failed air pressure generator. With a reduced crew, each of the miners has had to spend some time alone in the mine, leaving them with an uneasy feeling that they aren't really alone in there. Jamol is moving ever closer to losing his greenhorn status when he's tasked with taking the mucker to clear out debris from their latest blast.
Meanwhile, at Hell's Canyon, the ring of motion detectors surrounding Patrick and Kristen's base camp begin to sound, each in succession as if something was walking around their camp. As they investigate, Patrick is overcome by an unseen force that leaves him virtually incapacitated for the night.
At the mine, with Jamol on the mucker, things quickly spiral out of control when the mucker suddenly catches fire in the mine. As the flames spread, it's become a matter of life and death for the miners still trapped in the mine.
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.