Winter blankets the wreckage of the world. In the snow-covered ruins, four children scavenge for supplies to feed their dwindling group of survivors. Four, because Ian is gone – captured or killed by the mechanical death squads that hunt them all. SAM, his robotic guardian angel, has left as well. And without Ian, without his optimism, the survivors are losing hope. Until, one day, they recover the electronic device that their friend had built to communicate with SAM.