Son of the White Mare (or Feherlofia, in its original Hungarian) is based upon a Hungarian folk tale of the same name and is true to its source. Fanyuvo – or, in English, “Treeshaker” – is the third son of a mare, who is told he will one day tear a tree out from the ground. As he grows, she entertains him with myths of a magical world ruled by the Rain King and Ice Queen, as well as their three sons, who beg their parents for wives. After years of happiness, the three wives grow curious about the room that the King forbids them from opening; their curiosity, however, unleashes monsters into the world: three dragons, each one worse than the other, who kidnap the princesses to make them into their wives. The princes were killed, and the queen was turned into the mare and imprisoned. Upon her escape, she flees to a hollow tree, where she gives birth to Fanyuvo. After being nursed by the mare until adulthood, he finally achieves the goal of tearing out the hollow tree, only for the mare to die from exhaustion. It is here that he decides to travel out in the world and meets his two brothers: Komorzsolo and Vasgyuro – Stonecrumbler and Irontemperer, respectively.

Together, the three search for the entrance to the underworld and eventually discover it beneath a tree. Fanyuvo travels down within the underworld and discovers three castles, each inhabited by the dragons and their kidnapped princesses. The three dragons – three-headed, seven-headed, and twelve-headed – each represent the passing evolution of humanity: the stone age, with stone and copper tools; an oil-guzzling metal monstrosity akin to a tank, symbolizing wars of the early 20th century in all their senseless destruction; and third, a twisted amalgamation of a city skyline with eyes that light up like the windows of skyscrapers. Fanyuvo bravely battles each of them and defeats them with ease and collects their castles in the form of apples.

Once the three princesses are rescued, he raises them up into the upper world with the help of Komorzsolo and Vasgyuro pulling them up from above. Afterward, he attempts to send the apples back up to his brothers, only for the rope to snap and the entrance to seal, leaving Fanyuvo trapped in the underworld. Fanyuvo, shocked and upset, believes that Komorzsolo and Vasgyuro purposefully stranded him there, and decides to seek out a griffin that can take him back up so that he may get revenge. In order for the griffin to take him back up, he kills a snake that was threatening its chicks. Even so, the griffin is too weary and old to take him up, so as Fanyuvo and the griffin fly, he feeds the griffin oxen and wine to keep it moving – yet, as they traverse closer, Fanyuvo runs out of oxen and wine, and in a moment of desperation, sacrifices his legs to give the griffin enough energy to reach the top.

Moved, the griffin gives him back his legs so that he may confront his brothers. At first, he is infuriated at what he assumed had transpired but eventually begs forgiveness for ever hating them. He is forgiven, and the three return to their wives and their home. They live happily, and eventually pass away; in the end, the spirit of Fanyuvo is seen wandering the earth, lamenting the fact that it has been ravaged by humanity. He can see the stars in the sky and reflects upon their natural beauty, but they, too, are eventually swallowed up by smog until there is nothing more.