In the midst of the Mexican-American War, Captain John Boyd is reassigned to a remote military outpost in the Sierra Nevada Mountains after displaying unexpected acts of cowardice and heroism. His new station, Fort Spencer, is manned by a small, eclectic group of soldiers. Shortly after his arrival, an enigmatic stranger named Colqhoun stumbles into the fort with a harrowing tale of his party being stranded in the mountains and eventually resorting to cannibalism for survival. The fort's commanding officer, Colonel Hart, organizes a rescue mission, believing there may still be survivors.

As the rescue team ventures deeper into the wilderness, they uncover unsettling evidence supporting Colqhoun’s story and realize they might be in greater danger than anticipated. Colqhoun's intentions soon become increasingly suspect, leading to tension and paranoia among the soldiers. They must confront not only the chilling realities of survival cannibalism but also their own primal instincts. As Boyd grapples with his past cowardice and the horrifying events unfolding around him, he is forced into a desperate struggle for survival in both body and spirit.