Cole Franklin, an American mercenary, is recruited as a hired gun and guide at the remote outpost of Fort William, which is struggling to survive the decline of the fur trade. With dwindling supplies, the keepers of the Fort blackmail Cole into leading a trading party to a nearby Indigenous village where they discover a massacre and encounter the remaining half-crazed inhabitants for the bloodshed. Though the trading party survives with minimal losses and returns to the Fort with a bonanza of food and furs, the supernatural force responsible for the carnage follows them back.

As the casualties stack up, it becomes evident that something unnatural is driving the residents insane with murderous hunger. The rag-tag band of survivors forces Cole to put his military expertise to use in organising their last stand against what can only be described as some kind of madness.