E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Robert le Diable.
The son of Bertha and Bertramo. The former was daughter of Robert, Duke of Normandy, and the latter was a fiend in the guise of a knight. The opera shows the struggle in Robert between the virtue inherited from his mother, and the vice imparted by his father. He is introduced as a libertine; but Alice, his foster-sister, places in his hand the will of his mother, which he is not to read till he is worthy. Bertramo induces him to gamble till he loses everything, and finally claims his soul; but Alice counter-plots the fiend, and finally triumphs by reading to Robert the will of his mother. (Meyerbeer: Roberto il Diavolo, an opera.)