Seeking adventure, young Mateo Casillas explores a remote, legendary cenote in Yucatán, only to be pulled by a powerful underwater current into an unknown subterranean world. His disappearance sparks a rescue mission that discovers not just Mateo, alive, but a vast, unmapped cave system inhabited by the 'Keepers of the Way' – descendants of ancient Maya who retreated underground centuries ago.

The 'Keepers', who worship the goddess Ixchel and possess unique knowledge of cave ecology and healing flora, view Mateo as the "Sun-Touched," a figure from their legends whose arrival heralds great change. As a complex official expedition establishes contact and negotiates for Mateo's return, they uncover evidence of groundbreaking medicinal compounds derived from the cave's unique lifeforms.

However, the situation is complicated by the presence of a second, hostile group known as the 'Stone Breakers' or 'Children of Ah Puch'. This aggressive faction, seemingly locked in conflict with the 'Keepers', wields terrifying power by manipulating the cave's natural hazards – poisonous gas pockets, flash floods, rockfalls – through rituals dedicated to death gods.

While the official expedition grapples with first contact ethics, environmental dangers, and the threat of the Stone Breakers, a desperate trio from the surface embarks on an illegal expedition through a different entrance, hoping to steal valuable plant samples. They inadvertently stumble into the Stone Breakers' territory, triggering a desperate fight for survival.

"The Sun-Touched" explores themes of discovery, cultural collision, survival, and the ethical complexities that arise when the modern world encounters a lost civilization possessing both ancient wisdom and unique dangers, all centered around a young man caught between worlds.