The Castle of Otranto by Horace Walpole

Conrad is crushed to death on his wedding day by a gigantic helmet that falls on him from above. Manfred, lord of the castle, terrified that his son's death signals the beginning of the end for his line, resolves to avert destruction by re-marrying himself while divorcing his current wife Hippolita, who he feels has failed to bear him a proper heir.