Manfred is one character whose zeal for satisfying his own lust for power leads to his downfall. The conflict in the novel revolves around the issue of establishing the rightful heir to the throne of Otranto. Manfred is at the centre of this conflict. He is afraid of losing the throne to its rightful owner due to an ancient prophecy: That the Castle and lordship of Otranto should pass from the present fiarnily whenever the real owner should be grown too large to inhabit it.
Manfred's fear is that Conrad's accidental death might be an ominous sign of the beginning of the end for his line. In a swift move to avert destruction, Manfred,makes up his mind to divorce Hippolita, his wife, and marry Isabella himself Hippolita's crime is that she has failed to give him a suitable heir to the throne. Isabella escapes to the church with the aid of Theodore. The hint Manfred receives from Friar Jerome that Isabella is safe but might be in love with another man, makes him plot to kill Theodore. Friar Jerome's discovery of a marking below Theodore's shoulder adds a twist to the drama, as Theodore turns out to be Jerome's son. Taking advantage of this, Manfred gives Jerome a choice to make; either to give up the princess or his son's life. The arrival of an armed mysterious knight from another kingdom who wants to deliver Isabella intensifies the situation.
The race to find Isabella and Manfred by the knights in the underground church intensifies the situation as Theodore, who had been imprisoned by Manfred, has regained his freedom through Matilda Theodore hides Isabella in a cave and blocks it to prevent Manfred from getting to her, and ends up fighting one of the mysterious knights, who turns out to be Frederic, Isabella's father. Frederic's sudden love for Matilda, Manfred's daughter, adds more zeal to Manfred's quest for sexual gratification. Manfred begins to strike a deal with Frederic about marrying each other's daughters. Suspecting that Theodore is meeting with Isabella in the church, Manfred takes a knife into the church and strikes Matilda, mistaking her for Isabella.
In a nutshell, it is Manfred's lust for power and also sexual gratification that spells his own doom.
Points to Note:
(I) Struggle for ownership of the Castle (of Otranto)
(2) Manfred's struggle to overturn an ancient prophecy.
(3) Manfred's attempt to divorce Hippolita for not giving him a suitable heir.
(4) Manfred's attempt to marry Isabella
(5) Manfred's treatment of Theodore as a rival.
(6) Manfred's killing of Matilda, his own daughter.