To fulfill a promise he made to his late wife, Henry, an introverted widower, pursues an unlikely friendship with Millie, an independent but troubled teenage girl. Millie asks Henry to use his talent as an architect to help her with a strange goal: to build a raft that to sail across the ocean and find her long lost father. Despite pressure from people in Henry's professional and personal life to move on and reengage with his old way of living, Henry agrees to help her, enlisting two of his company's construction workers to help build the raft. As the bond between them grows, Henry and Millie discover that their friendship is the key to overcoming their losses. Together, this quirky and unexpected family embarks on an incredible adventure.