Prudence Lucas, as well as sharing these interests, designed the costumes and sets for the first production (1938) of his Icelandic tragedy "The Lovers of Gudrun". Her nervous breakdown in 1938 is touched on in Lucas's "Journal Under the Terror, 1938" (1939); Lucas sought help from, among others, Wilhelm Stekel, whom he met in London in 1939, but the rift proved irreparable. The emphasis on psychology in his post-war books – "Literature and Psychology" (1951), "Style" (1955), "The Search for Good Sense" (1958), "The Art of Living" (1959), the essay on 'Happiness' in "The Greatest Problem" (1960), "The Drama of Ibsen and Strindberg" (1962) – reflects an interest shared with his third wife (1940–1967), the Swedish psychologist Elna Kallenberg (1906-2003), whom he married in 1940 – "the stranger who came to me from beyond the sea when I most needed her" (Elna Kallenberg had flown from Sweden, with special permission from the Home Office, to join him in late 1939). They had two children, Signe and Sigurd.