In the heart of the Bob Marshall Wilderness, two sisters set out on a skiing adventure up a looming mountain. But they never returned, leaving behind a trail of fear and uncertainty. Colter Shaw, an old friend, received a call about the missing sisters and set out to find them. The fears of their demise or injury were soon realized when Colter stumbled upon Shelly, her head battered against a rock and hallucinating from the cold. She had disrobed in her delusion of warmth, and Colter rushed to her rescue before she succumbed to the element's embrace.
Brianna, Shelly's sister, was also discovered unharmed but determined to seek help after a strange encounter with a figure wearing antlers. Colter, now more concerned with keeping the sisters warm, sent McLaren to fetch the snowmobiles and phones while he kept watch over them.
As McLaren was away, Colter discovered an unexpected presence on the mountain – a cabin with inhabitants who claimed to be devoid of communication devices. But they did possess snowmobiles, including one with a sled large enough to carry Shelly. The discovery proved pivotal in their rescue and safe return to the cabin.
Colter's radio remained silent as the morning approached, prompting him to set out in search of McLaren. The hunt led him to a wounded McLaren, trapped by an unseen trip wire. Before he could assist, a bullet whizzed past them, leaving Colter focused on safety rather than the shooter's identity. With McLaren safely returned to the cabin, they found everyone gone – including the sisters – and the truth emerged: they had not gone skiing, but rather embarked on a documentary investigation into the "deadzone" mountain's mysterious disappearances.
Randy's concerns about Colter's absence were met with disbelief from Reenie and Bobby, who were unaware of the true nature of the mountain and its inhabitants. But Colter's realization that the trio had abducted and killed the cabin's owners, including Amelia – a woman held hostage for nine years by the cult led by Father Ammon and his sons Rufus and Dash – brought a new urgency to their rescue mission.
Amelia's ordeal had left her convinced that all men were dangerous, including Colter himself. But he was able to convince her otherwise and with her help, they fought off the cult members and saved all the women from their cannibalistic clutches. The chopper arrived just in time to carry them off the mountain, including McLaren, leaving Reenie to regret her role in bringing them to this place and its horrors.
