In Baja California, the newborn grey whale calves spend their first months of life in the safety of the San Ignacio lagoon, suckling and learning swimming skills. At the lagoon, Nigel talks to the scientists who are studying the whales and finds unexpected birds of prey nesting at the water's edge. As the whales start their journey north towards the border with the USA, he takes a parallel road trip.

The whales' journey takes Nigel right up the coast of California, where the hustle and bustle of human activity is a stark contrast to the peace of the Mexican desert. He goes swimming and encounters humpbacks in the Santa Barbara Channel, is led on a merry dance by a unique, diminutive fox on the island of Santa Cruz, and spots Californian condors above Big Sur.

As the whales swim further into the cold seas of the Pacific Northwest, Nigel joins the Quileute tribe for their annual whale-welcoming ceremony. On the beaches of Whidbey Island, he digs up some fascinating information about grey whale feeding habits. Heading across the Canadian border, Nigel follows the whales to Vancouver Island, where he witnesses a frenzied killer whale attack.

On the Pribilof Islands off the west coast of Alaska, Nigel sees puffins, cormorants, Arctic foxes and fur seals. Further north, the native Yupik people take him on a midnight boat ride around St Lawrence Island. Back on the mainland, Nigel finds herds of musk ox on the outskirts of Nome before flying to Barrow, the most northerly city in the USA.