As 300 million salmon start to invade Alaska's rivers, this is the most critical time for thousands of bears, eagles, wolves and whales as the great summer feast reaches its climax. Matt joins the salmon as they reach the finish line of their incredible journey. Will the family of black bear cubs get enough food to survive the coming winter? Liz is in the wildest, remotest part of Alaska hoping for a live TV first - an encounter with wolves joining the largest protected population of brown bears in the world and jostling for fishing position on the river. Steve heads out to sea and into the epicentre of the action as orcas join the feast and humpback whales come together to hunt in one of the most impressive sights in the natural world.