What was the title of C.S. Lewis’s final completed novel in the Ransom Trilogy?

That Hideous Strength was the final completed novel in C.S. Lewis’s Ransom Trilogy.

Published in 1945, That Hideous Strength concludes the trilogy that began with Out of the Silent Planet and continued with Perelandra. The protagonist is Mark Studdock, an academic drawn into the National Institute of Coordinated Experiments, or NICE. The novel combines social satire, science fiction, Arthurian material, and Christian ideas about power and corruption.

The earlier books focus more directly on the interplanetary adventures of Elwin Ransom. In the final novel, the action is centered on Earth, particularly in England. Ransom still has an important role, but the narrative’s setting and concerns are broader than those of the first two volumes.

The title comes from a passage in David Lindsay’s 1920 novel A Voyage to Arcturus, a work Lewis admired. Readers sometimes call the trilogy the Space Trilogy even though its final volume is much more concerned with institutions, ideology, and spiritual conflict than with travel between planets.