The mysterious warning

"The good old Count Renaud is dead, and his will makes the degenerate Rhodophil his heir, disinheriting his other son Ferdinand, who has married against his father's wishes. Rhodophil promises to share his new riches with his younger brother and his wife Claudina, but Ferdinand hears a mysterious voice from beyond the grave, warning him to flee his brother and his wife to save himself from sin and death!"--Goodreads.