Which C.S. Lewis novel is the third and final book of the Space Trilogy?

That Hideous Strength is the third and final novel of C.S. Lewis’s Space Trilogy.

Lewis published That Hideous Strength in 1945, following Out of the Silent Planet and Perelandra. Unlike the first two novels, much of its action takes place on Earth, where a secretive institution seeks power through a mixture of technocratic ambition, manipulation, and occult influence.

The novel’s subtitle, “A Modern Fairy-Tale for Grown-Ups,” signals its blend of modern social criticism, medieval symbolism, and speculative fiction. Lewis was responding in part to ideas about science and social planning that he believed could reduce human beings to objects of control.

The trilogy is sometimes called the Ransom Trilogy, after its central character, Elwin Ransom. That Hideous Strength is the concluding volume, not the opening novel; Out of the Silent Planet begins the sequence.