Every fall in the northern Pacific up to a million salmon migrate back to the rivers and streams where they were born to spawn. Many of these streams are located in Katmai National Park Alaska. It’s here where a massive population of coastal brown bears gather to eat these fish.

The crew heads inland to a section of the river to observe the many different families as they fish. Along their path they have an intimate encounter with a mom and her three cubs. They arrive at their destination and see many bears that they have already met as well as some new faces.

Everyone hates biting insects but if you look closer you can see that even the tiniest and most irritating bug can be essential for a working ecosystem. During a lull in bear and salmon activity Casey and the crew decide to head inland in search of the spawning fish.

After seeing a wolf in the distance and tracks on the shore the crew head inland in search of more clues to the wolf's whereabouts. They encounter a familiar bear family on their way and decide to follow them to a local fishing spot where a large number of bears have gathered.

Casey and the crew go out in search of the family of the lost cub from the previous night. They hope that if they find them the cub will have found them as well.

As the end of their expedition draws near salmon and bear activity begins to decline but that doesn’t mean that there aren’t some bears still lingering around the area. Casey and his crew wander the tidal flats and interior of Katmai and find the bones of a humpback whale that washed ashore.