Caspak

The Land that Time Forgot - In the South Pacific is a mountainous island called Caspak. Winged humanoid creatures, dinosaurs, ferocious beasts of prey, Neanderthals, "wild ape-men," and monstrous reptiles terrorize each other, and the mixed crew of WW 1 adventurers fight across the island.

The People that Time Forgot - Ex-cowboy Tom Billings leads a rescue mission to save Bowen Tyler, the protagonist of The Land That Time Forgot. In the midst of hair-raising adventures, he has more trouble keeping his own skin intact than in finding his friend.

Out of Time's Abyss - The Lost world saga continues. It connects the previous two installments, bringing in characters introduced in each. Burroughs completes the revelation of his lost world's unique biological system, only hinted at in the previous installment, in which the slow progress of evolution in the world outside is recapitulated as a matter of individual metamorphosis. This system forms a thematic element serving to unite the three Caspak stories.