“Marathon Boy” follows the unbelievable story of Budhia Singh, a boy born into the crushing poverty of an Indian slum, sold by his destitute mother, and rescued by a judo coach who runs an orphanage. The coach, Biranchi Das, soon discovers that then-three year-old Budhia has a prodigious talent for running. Jumping on what he sees as a huge opportunity both for himself and the children who depend on him, Das promotes Budhia to the Indian media as a boy wonder, an expression of the unquenchable Indian spirit. By the time he is four, Budhia has run twenty half-marathons and 48 full marathons.

Buoyed by Budhia’s inexhaustible willpower Das stages one hell of a publicity stunt: a 42-mile run, which could set a new world record.

Director Gemma Atwal does a masterful job, in this HBO production, of allowing the story to play out in front of her without prejudicing it.