Which 1945 C.S. Lewis novel concludes the Space Trilogy?

That Hideous Strength is the 1945 novel that concludes C.S. Lewis’s Space Trilogy. Unlike the first two books, much of its action takes place on Earth, where a modern scientific institution pursues power through the organization called N.I.C.E.

The novel follows Mark and Jane Studdock as they are drawn into opposing visions of technological and spiritual control. Elwin Ransom, the protagonist of the earlier books, also returns, although the story’s focus shifts toward Britain and its institutions.

The trilogy begins with Out of the Silent Planet in 1938 and continues with Perelandra in 1943. That Hideous Strength was published last in 1945. Its title comes from a line in David Lindsay’s 1920 novel A Voyage to Arcturus, another work that influenced Lewis’s imaginative writing.