In a London fog, late at night, by accident two men meet on a deserted street. One is John Chilcote, member of the House of Commons and an unfortunate victim of drug addiction. The other is John Loder, a struggling freelance political writer. In the wan illumination of the street-light the men discover they are exact doubles in appearance. Loder agrees, for money, to impersonate Chilcote and the men temporarily change places in life.