Our film begins in high summer in Hudson Bay in Canada's Far North, where polar bears have learned to ambush beluga whales, which visit warm river estuaries to breed. It's a crucial time window, at a difficult time of year. In the vast swathes of tundra, a pair of Arctic foxes gather and bury snow geese eggs, and hunt the chicks, for their fast-growing pups. And in Canada's Bay of Fundy, which has the most extreme tides on Earth, vast flocks of semi-palmated sandpipers arrive on their journey from the Arctic to South America, to feed on mating mud shrimps. But they must beware of hunting peregrine falcons.