Lambert Strether, a mild middle-aged American of no particular achievements, is dispatched to Paris from the manufacturing empire of Woollett, Massachusetts. The mission conferred on him by his august patron, Mrs. Newsome, is to discover what, or who, is keeping her son Chad in the notorious city of pleasure, and to bring him home. But Strether finds Chad transformed by the influence of a remarkable woman; and as the Parisian spring advances, he himself succumbs to the allure of the 'vast bright Babylon' and to the mysterious charm of Madame de Vionnet.