The novel features a muscular hero known on earth as Esau Cairn, a complete misfit in modern America who "belongs in a simpler age".

Realizing there is no future for him on Earth, Cairn asks help from a scientist friend, who teleports him to the recently discovered alien planet of Almuric, a savage but habitable world in another universe.

Eventually he stumbles upon the native people of Almuric, the Guras, who are hairy, ape-like men with a violent but pragmatic way of life.

Cairn begins to enjoy this new, simpler and truer existence, and his strength and fighting prowess earn him the nickname Ironhand.

Cairn and Altha are captured by Yagas and taken to their "black citadel of Yugga, on the rock Yuthla, by the river of Yogh, in the land of Yagg".

Discovering a secret tunnel unknown to most Yagas, Cairn returns to the Guras and persuades them to stop infighting and unites them against a common enemy.

Cairn leads a combined army of Gura warriors to Yugga through the secret tunnel, taking the Yagas by surprise.