Which C.S. Lewis novel is the final volume of the Ransom Trilogy?

That Hideous Strength is the final volume of C.S. Lewis’s Ransom Trilogy. The novel was published in 1945, following Out of the Silent Planet from 1938 and Perelandra from 1943.

Unlike the first two books, which are largely planetary adventures, That Hideous Strength is set mainly on Earth. Its plot concerns the National Institute of Coordinated Experiments, or N.I.C.E., and its attempt to use scientific and bureaucratic power for sinister ends. Elwin Ransom remains an important figure, although the novel has a broader cast.

The trilogy is also called the Space Trilogy or Cosmic Trilogy. The title comes from a line in the medieval poem The Song of the Faerie Queene by Edmund Spenser, linking Lewis’s modern satire with older literary traditions.