When a bad storm throws Bangor, a harbor porpoise, off course, he finds himself all alone in the harbor of Ogunquit, Maine. And he's not the only one who's lost in these wayward waters: Lars, a rowdy pup, is knocked overboard a nearby boat. With the help of a girl named Natalie, Bangor rescues Lars, and they become fast friends.

But not everyone in the small town approves of this unlikely friendship. Some find Lars a nuisance to the community, and it isn't safe for Bangor to remain in the harbor. It's up to Natalie to convince the town to locate Bangor's pod and return him safely home -- even if it means saying goodbye to her new friend.