Karl May's In the Cordilleras follows a perilous expedition across the harsh and unpredictable landscapes of South America, where the advancing group moves toward the Pampa de Salinas and is soon drawn into a conflict that blends rescue mission, pursuit, and moral conflict. The journey becomes urgent when they encounter Pena, who pleads for help for settlers threatened in Aripones territory, revealing a wider network of danger controlled by hidden interests and local power struggles.

As the travelers respond to this call, suspicion falls on the sendador Geronimo Sabuco, a shadowy figure whose influence seems closely tied to the settlers' plight. The group succeeds in capturing him and rescuing the endangered settlers, but the situation quickly becomes morally complicated. While companions such as Gomarra and Pena demand harsh punishment, the narrator takes a more restrained and secretive approach, releasing Sabuco in the belief that a different resolution might be possible. This decision shifts the balance of the expedition, introducing a deeper layer of unpredictability to the journey.

Sabuco's reaction to his release escalates the danger dramatically, as he turns against the group and incites hostile forces to attack them, resulting in the capture of most of the travelers. Only the narrator and Pena manage to escape, continuing their struggle through an increasingly hostile environment where trust is fragile and survival depends on constant vigilance.

As the expedition continues, the narrator is also forced to attempt a daring rescue of his captured companions, reinforcing the sense of responsibility and leadership that drives the story forward. Throughout the narrative, Karl May builds a layered adventure shaped not only by external dangers but also by conflicting moral choices, shifting alliances, and the constant uncertainty of life in the Cordilleras.