§ Of Beren and Lúthien The Silmarillion

But now a shadow fell upon the joy of Doriath at the return of Lúthien the fair; for learning of the cause of the madness of Carcharoth the people grew the more afraid, perceiving that his danger was fraught with dreadful power because of the holy jewel, and hardly might be overthrown. And Beren, hearing of the onslaught of the Wolf, understood that the Quest was not yet fulfilled.