The title comes from a passage in the Book of Revelation (22:5) which is quoted by Lunt's character in Act 3, Scene 6: There shall be no night there: They need no lamp nor light of the sun, for the Lord God gives them light.? The play is set in Finland between 1938 and 1940 and concerns a Nobel Prize-winning Finnish scientist (portrayed by Alfred Lunt, whose own stepfather was a Finnish-born physician) and his American-born wife (portrayed by Lynn Fontanne), both of whom are reluctant to believe that the Russians will invade their beloved Finland. But with the final advent of Finland's Winter War with the Soviets, their son Erik joins the Finnish army, and the scientist joins its medical corps. John Mason Brown wrote “No one can complain about the theatre's being an escapist institution when it conducts a class in current events at once as touching, intelligent and compassionate as There Shall Be No Night.”

According to William L. Shirer, Sherwood was inspired to write the play by William Lindsay White's moving Christmas broadcast from the Finnish front during the Winter War. The son of journalist William Allen White, the younger White had been sent there by CBS to report on that war.[5] Sherwood bases his American journalist (portrayed by Richard Whorf) in this play upon W. L. White, substantiating this in his preface to the first published edition by Charles Scribner's Sons in 1940.