What is the name of the final novel in C.S. Lewis’s Space Trilogy?

That Hideous Strength is the final novel in C.S. Lewis’s Space Trilogy. It was published in 1945 and follows the earlier novels Out of the Silent Planet and Perelandra.

Unlike the first two books, which focus heavily on interplanetary travel and alien worlds, That Hideous Strength is set mainly on Earth. Its story combines academic politics, scientific ambition, social manipulation, and supernatural conflict. The fictional National Institute of Coordinated Experiments, or N.I.C.E., represents a powerful organization pursuing control through supposedly rational progress.

The trilogy is also called the Ransom Trilogy, after its protagonist, Dr. Elwin Ransom. The final novel is sometimes confused with Lewis’s unfinished or posthumously published science-fiction material, but That Hideous Strength is the trilogy’s published conclusion.