Asa Butterfield plays Nathan Ellis, a young teen who's exceptionally good at math. His supportive and understanding father died when he was nine. His mother (Sally Hawkins) is also very supportive, but doesn't understand him quite as well as his dad did. They find a tutor for him in the depressive and slightly foul-mouthed Martin (Rafe Spall) who is a former Math Olympiad competitor. Nathan is also recruited to the Math Olympiad, and is sent to training in Taiwan - which pushes him way out of his comfort zone.
Butterfield and Hawkins are both good, but Spall steals every scene he's in and Marsan is also more memorable (as the obnoxious British team coach) than the two leads. Considerably better than your average uplifting-story-of-the-week, but - despite being "based on a true story" or "inspired by a true story" or whatever it is - I enjoyed it but the movie doesn't manage to achieve greatness.