Environmentalist Leanne Allison and wildlife biologist Karsten Heuer follow a herd of 120,000 caribou on foot, across 1,500 kilometres of rugged Arctic tundra. The husband-and-wife team wants to raise awareness of threats to the caribou's survival. They let the caribou guide them through a wild and remote landscape, from the central Yukon to coastal Alaska and back. During the five-month journey, they ski and hike across mountains, swim icy rivers, brave Arctic weather and endure hordes of mosquitoes. They survive an encounter with a hungry grizzly bear that forces them to reconcile what it means to be a part of true wilderness. Hunger, fatigue and pain become routine, but the sacrifice is worth it when they witness the miracle of birth just metres from their tent. Dramatic footage and video diaries provide an intimate perspective of an epic expedition. At stake is the herd's delicate habitat, which could be devastated if proposed oil and gas development goes ahead in the herd's calving grounds in Alaska's Arctic National Wildlife Refuge.