l and Ellie grow old together, and then she dies.

Carl is left alone in their house, surrounded by a building site. A developer wants him to move. He refuses but then his anger gets the better of him. On the day they show up to take Carl away, he unfurls thousands of balloons, and he and his house float up, up and away. But he has a stowaway. A tubby boy scout called Russell. The adventure of this odd couple begins.