The Fourth 'R' follows a five-year-old boy named Jimmy Holden, who was given the equivalent of a college education by virtue of his parents' invention, an "Electromechanical Educator." At the beginning of the story, Jimmy's mother and father are murdered by their best friend, who is also the youngster's godfather and appointed guardian as well as the inventors' trustee. Jimmy must survive his guardian's efforts to squeeze the secret of the invention out of him (whereupon his death will most certainly be arranged, just as his parents' were), and then escape into hiding until he can grow into a physical stature commensurate with his mental age.