George Arliss is the millionaire of the title, a retired auto tycoon who's been ordered by his doctor to rest and avoid exercise. Arliss is shaken out of his sedentary existence by an insurance salesman who advises him to pick himself up and enjoy life. The old man heads to California, where he conceals his identity and goes to work for a service station. Given a new lease on life, the millionaire amuses himself by playing matchmaker with his own daughter (Evelyn Knapp) and the go-getting young service station manager (David Manners). Barely distinguishable from George Arliss' other non-historical vehicles, The Millionaire is given an added dimension by James Cagney, who shows up for three wonderful minutes as the friendly insurance agent.