In Defiant Agents (Version 2) by Andre Norton, readers are taken on a thrilling adventure through time and space. The story follows a group of three agents who are sent back in time to a prehistoric world, where they must survive and find a way to stop an alien race from taking over Earth. The characters are well-developed and the plot is full of twists and turns that keep you on the edge of your seat. Norton's writing is engaging and paints a vivid picture of the dangerous world the agents find themselves in. Overall, Defiant Agents (Version 2) is a gripping science fiction novel that will keep you hooked from beginning to end.

Book Description:
Operation Cochise: a carefully planned Western move to colonize a planet ahead of the Reds. Travis Fox had been an eager volunteer, but the morning he dragged himself half-conscious from the wrecked spaceship on the planet Topaz, he sensed the terror which would threaten the project. Travis never learned why the ship had crashed, nor why he and the other Apache agents had been shot into space without warning and under Redax control, a machine which had returned them to ancestral mentality. But the dangers on Topaz demanded free minds, for Travis soon realized that if the Reds already encamped beyond the mountains--a horde of barbaric Mongols completely dominated by their masters--discovered the secret of the eerie underground chamber in the towers hidden in a valley of mists, not only Topaz but Terra itself would be destroyed.