In a post-apocalyptic future, Earth has been overrun by a new ice age, forcing humanity to take refuge in a series of underground colonies scattered across the desolate landscape. The constant battle with the cold, disease, and dwindling resources turns each day into a struggle for survival. Colony 7, led by the wise but ailing Briggs and the resourceful Mason, receives a distress signal from Colony 5, their closest known neighbor, prompting a reaction fraught with uncertainty and fear. The perilous weather conditions make communication almost impossible and travel extremely dangerous. Despite the risks, Briggs decides that they must respond to the call for help and mounts a small expedition team to investigate. Included in this team is Sam, a skilled engineer and a younger denizen of the colony, who shares Briggs' sense of responsibility for their fellow survivors.

Upon reaching Colony 5, the small team is confronted with a horrifying discovery, a threat far more vicious than the cold or starvation they have grown accustomed to battling. As they uncover the truth, they must make quick decisions, for their own survival and potentially the future of humanity itself. The dire situation tests the limits of their morality, forcing them to question the value of life and what it means to be civilized in a world where the environment has turned against humanity. The fear of what they have found follows them back to Colony 7, bringing greater risks than they could have imagined.