Dr. Elwin Ransom embarks on a remarkable journey that is literally out of his world, but not simply because he desired so. The protagonist gets captured by a maniacal physicist called Weston and his accomplice Devine into their spaceship, sending them off to a neighboring planet called Malacandra - or what humans would call Mars. The two plan to offer the victim as a sacrifice to the Malacandrian kind, but Ransom overhears their conversation on the shuttle. He escapes their grasp immediately after the spaceship lands on the red planet, deep into the forest away from Weston and Devine.
Ransom spends the following days meeting the three different races on Malacandra: the hrossa, séroni, and pfifltriggi. He encounters his first hross, then follows it to its home. Ransom learns to abide by their culture and speak their language, which increases his understanding about their world as well as their trust in him. Hyoi, one of the hrossa, teaches Ransom the cores of each race: the hrossa are known for their fishing and poetry, the séroni for their wisdom, and the pfifltriggi for their handwork. Hyoi and his tribe even invites Ransom to a hunt to express their honor, but it does not end well. The hross dies to a gunshot wound, coming from Weston and Devine in the forest. The other hrossa tells Ransom that their god, Oyarsa, calls for his presence, and sends him off on a difficult and dangerous journey.
A sorn with the name of Augray takes Ransom on the rest of his way to Oyarsa. Ransom initially thought Weston and Devine were going to give him to the séroni as a sacrifice, but Augray clears the misunderstanding. He tells the sorn about Earth, and in return he learns the brief history of Malacandra. The conversation helps realize that the three races live in unity under Oyarsa's rule - resulting in a planet with absolutely no bloodshed.
The trial begins a day after Ransom's arrival in Meldilorn. The hrossa bring in Weston and Devine, who have been captured after Hyoi's death. Oyarsa enters in his vapor-like form before the three human beings, and he begins to decide their fate.
