Mr. Topaze is an unassuming school teacher in an unassuming small French town, who is honest to a fault. He is fired when he refuses to give a passing grade to a bad student, the grandson of a wealthy baroness. Castel Benac, a government official who runs a crooked financial business on the side, is persuaded by his mistress, Suzy, a musical comedy actress, to hire Mr. Topaze as the front man for his business. Gradually, Topaze becomes a rapacious financier who sacrifices his honesty for success and, in a final stroke of business bravado, fires Benac and acquires Suzy in the deal. An old friend and colleague, Tamise questions him and tells Topaze that what he now says and practices indicates there are no more honest men.

When her father dies, Epifania Parerga, an Italian in London, becomes the world's richest woman. She feels incomplete without a husband and falls in love with a humble, Indian physician, Ahmed el Kabir, much loved by his indigent English patients.

A czarist captain stops at nothing to learn the secrets of a countess rumored to have sold her soul to the devil in order to always win at cards.