Earth, the cinema release of the awarding-winning TV series Planet Earth.

Starting in the high Arctic in January, as the darkness of winter gives way to the sun, a mother polar bear is shown emerging from her den with two new cubs.

She needs food and must lead her cubs to her hunting ground on the sea ice before it begins to break up. By April, the sun never sets, and by August all the sea ice has melted.

The mother and cubs have retreated to dry land, but a male polar bear is trapped at sea and must seek out land by swimming. He reaches an island with a walrus colony but is too exhausted to make a successful kill. He dies from injuries sustained in a walrus attack.