Which 1945 C.S. Lewis novel features Mark Studdock?

That Hideous Strength features Mark Studdock as its central male character.

Published in 1945, That Hideous Strength is the third novel in C.S. Lewis’s Ransom Trilogy. Mark Studdock is a sociologist who becomes involved with the National Institute of Coordinated Experiments, or N.I.C.E., an organization whose scientific and political ambitions conceal a deeper danger. His wife, Jane Studdock, has disturbing dreams and follows a separate path connected with Ransom and his community.

Unlike the first two books, which focus strongly on planetary settings, this novel is set mainly in an English university town and countryside. It combines social satire, science fiction, Arthurian elements, and Christian ideas. The title alludes to a line from a seventeenth-century poem by David Lyndsay. That Hideous Strength should not be confused with the trilogy’s opening novel, Out of the Silent Planet, or its middle volume, Perelandra.