Consider the premise. Lizzie, played sensitively by the impressive actress Emily Mortimer, is raising her deaf, 10-year-old son Frankie alone, as she long-ago left her abusive husband whom Frankie doesn’t remember. They live with Lizzie’s mother, Nell (Mary Riggans). Jack McElhone, an astonishingly good young actor, is endearing without being the least bit cloying as Frankie, who has learned to cope with his hearing impairment but must struggle in school to get on equal footing with the others.

Lizzie has been maintaining a fiction. To meet Frankie’s need for a dad, she has pretended to him that his father is a seaman and she writes letters coming from the fictional father to Frankie and sends them to a post office box, and Frankie in turn writes back to his fictional dad to the same box. Lizzie’s mother frowns on the ruse. Frankie keeps a map on his wall tracking the movements of the ship Lizzie has said his dad is on—a name she made up. Lo and behold, there’s a real ship with that name set to dock in Glasgow, and Frankie looks forward to finally getting to meet his dad.

It is crisis time, and what Lizzie does and how it all develops flesh out the rest of the tale, better left for you to discover. The story gets complicated, with emotions and revelations involved. There is a fine role for actor Gerard Butler as The Stranger, and another good part well played by Sharon Small as Lizzie’s perky friend and employer Marie. All is handled with admirable restraint, enabling us to enjoy the performances and be carried along in the details of the events and the relationships without feeling unduly manipulated.