"Calcutta. Crap, I'm still in Calcutta."

“Lion” is the incredible true story of why you should never have children in India. Based on Saroo Brierley’s memoir “A Long Way Home,” the film, an inspiring drama that earns tears without jerking them, begins with 5-year-old Saroo (played by a bouncing ball of energy named Sunny Pawar) becoming separated from his mother and brother and ending up a thousand miles away in Calcutta. He doesn’t know his mother’s name, and he misremembers the name of his hometown. Oh, and they speak Bengali here, not Hindi. Oh, and apparently Calcutta is rife with child-snatchers who prey upon street kids, of which there are tens of thousands.

First-time feature director Garth Davis jangles the nerves with these early scenes, but don’t fret. Saroo is rescued soon enough, adopted by a saintly Australian couple, John and Sue Brierley (David Wenham and Nicole Kidman), who raise him up lovingly to become Dev Patel. (Patel gets top billing even though he’s only in the second half of the film. Get a good agent, kids!) Grown-up Saroo, tortured by the knowledge that his family never knew what happened to him, sets out to find them, with only his distant memories and Google Earth to assist him.

Saroo’s path may be unclear but the movie’s sure isn’t. Like the train that took him away in the first place, the film moves steadily toward its tearful destination, propelled by sincere performances and Volker Bertelmann and Dustin O’Halloran’s gently urgent musical score. Kidman shows great tenderness as the adoptive mother, underscoring the theme of “family” not being limited by biology, and Patel is serious-minded and haunted. But it’s little dynamo Sunny Pawar that you’ll remember best, his infectious cheer and Annie-like optimism encapsulating the film’s hopeful tone. The best part might be the broad smile that crosses your face when the movie finally explains why it’s called “Lion.”

B+ (1 hr., 58 min.; PG-13, child endangerment, mild profanity.)