The grandson of Ricardo accidentally stabs his daughter Matilda in the chapel, and the action of this novel begins when Conrad is crushed by a giant helmet.  
In this work, a portrait of one character's grandfather sighs and removes itself from its frame, and three drops of blood falling from the nose of a statue is taken as a sign that two characters should not marry.  A birthmark revealing one character to be the son of the priest is discovered shortly before an execution which is interrupted by the arrival of the Knight of the Gigantic Saber.  The grandson of Ricardo accidentally stabs his daughter Matilda in the chapel, and the action of this novel begins when Conrad is crushed by a giant helmet.  In the end, the giant Prince Alfonso reveals that Theodore is the true heir, allowing him to marry Isabella and forcing Manfred to abdicate.  FTP, name this Gothic novel by Horace Walpole.
In this work, a portrait of one character's grandfather sighs and removes itself from its frame, and three drops of blood falling from the nose of a statue is taken as a sign that two characters should not marry.  
The Castle of Otranto