The Castle of Otranto

Manfred, lord of the Castle of Otranto, is about to have his son, Conrad, married to princess Isabella. But when his son is mysteriously killed by a helmet thrown from above, the ominous words of an old prophecy seem to come to life. Now, in an effort to avoid the extinction of his family Manfred is decided to marry young Isabella himself. Will he manage to succeed on his purpose or are there greater forces behind the princess?