The story is set in 1890s Siam. Siang is a young Muay Thai warrior and rocketry expert who steals back water buffalo taken from poor Isan farmers by unscrupulous cattle raiders. He is searching for a man with a tattoo who killed his parents.
A local nobleman, Lord Waeng, wants to create a market for his steam tractors, so he hires a hulking convict, "The Thief", to kill all the cattle traders and round up all the water buffalo for slaughter, depriving farmers of the draft animals they need to cultivate rice. Lord Waeng's men are eventually pitted against Nai Hoi Sing, a cattle trader with supernatural martial arts powers and a tattoo on his chest. The tattoo gets Siang's attention, and while the Thief is attempting to steal Sing's cattle herd, Siang briefly confronts Sing but is repelled.
Lord Waeng consults the Black Wizard, who was once cursed by Sing so that he cannot withstand sunlight, to find a way to defeat Sing. The Black Wizard says the only way to reverse his spells is to use the menstrual blood of a virgin – the Black Wizard's daughter, E'Sao.