Having just lost their father to the deadly Snowman, sisters Milli and Mae Mae are forced to carry on their quest alone. Traveling farther from the safety of their village, they're taken in by a secret society of Trench dwellers who help them battle the Snowman, and Milli makes a decision that may have fatal consequences for Mae Mae--but sacrifices must be made to unravel the awe-inspiring secret of their family's past!