While sketching in Siena, Bernard Longueville meets Angela Vivian and her mother. Later, Bernard's friend and self-proclaimed "mad" scientist Gordon Wright calls Longueville to Baden-Baden to pass judgment on whether he should marry Angela. Bernard recommends against it, based on his belief that Angela is something of a mysterious coquette. So Gordon marries the lightweight (in both senses) Blanche Evers. After a couple years Longueville again meets Angela at a French beach resort and realizes he loves her. They get engaged, and Angela tells Bernard that she had refused Gordon when he proposed to her. Eventually Angela manages to reconcile Gordon and Blanche, who were becoming estranged due to a supposed extramarital affair Gordon had. Everybody lives happily ever after.