Teacher B.T. Cates is arrested for teaching Darwin's theories. Famous lawyer Henry Drummond defends him; fundamentalist politician Matthew Brady prosecutes. This is a very thinly disguised rendition of the 1925 "Scopes monkey trial" with debates between Clarence Darrow and William Jennings Bryan taken largely from the transcripts.

Middle-aged Madison Avenue advertising executive Roger O. Thornhill is mistaken for a government agent by a gang of spies. He gets involved in a series of misadventures and is pursued across the States by both the spies and the government whilst being helped by a beautiful blonde.