In 1972, Vincent Moretti (Eric Krogh) is incarcerated and sent to prison for fraud and murder. In jail, he meets Leonard "Leo" Caruso (Fares Fares), who has been inside for six months for grand theft, assault and armed robbery. While in the cafeteria, a thug sent in by crime boss Harvey tries to murder Leo, but Vincent intervenes, resulting in both of them being sent to the infirmary while the thug is beaten to death after stabbing and killing a prison guard. While in the infirmary, Leo requests Vincent's help to steal a chisel from the office. Vincent complies. After the theft, Vincent senses that Leo is planning an escape and offers to help. Leo initially refuses, but begrudgingly agrees to collaborate when Vincent reveals he has a grudge with Harvey.
After he was saved, Percy tried to tell him to stay at the ranch for his safety, but Nico yelled at Percy him what happened with Bianca, causing Annabeth to come to his defense. After arguing, Percy decided to help Nico summon Bianca's soul after Nico couldn't, telling him she sent him iris messages. That night, they went into the field to summon her, but it was interrupted by Minos, telling Nico to not trust Percy and his friends. Nico managed to order Minos to leave and the ritual continued. Bianca appeared, and Nico was overjoyed to see her, but she was sad, saying he gotten tall. Nico was heartbroken when she said that he hoped he'd given up on summoning her, saying Percy was right and he cannot hold grudges, since they were the fatal flaw for children of Hades. Nico became angry at her for helping Percy, but Bianca told him to stop blaming him for her choices, since she knows he is mad at her, and that it would be his doom. Bianca disappeared after Kronos stirred, saying she loved him and to remember what she said.
In The Titan's Curse, Nico is ten years old. He enjoys playing with his Mythomagic cards that none of the others truly seem to understand. The Blood of Olympus reveals that he was obsessed with pirates even before that. He is clueless and very inquisitive. He likes Percy a lot as a big brother figure, but The House of Hades reveals that Nico had developed secret romantic feelings for him. Young Nico annoys Percy with his ceaseless questions, especially when he asks if Annabeth Chase was his girlfriend, which makes Percy consider "stuffing him in a meat-flavored sack and throwing him to the wolves." He is excited about finding out that he is a demigod (immediate response: "Cool!"), and starts to compare monsters to Mythomagic creatures. He feels abandoned when his sister Bianca, who practically acts as his parent, becomes a Hunter of Artemis. When she goes on a quest, Nico makes Percy promise to protect her. After her death, he develops a long-lasting grudge toward Percy for letting her die. Once he realizes that he is a son of Hades, he casts away his childhood interests and runs off on his own.
Nico di Angelo's fatal flaw is holding grudges, as Bianca's ghost tells him. In his case, it can lead to not wanting help or not asking to be saved in deadly situations because he simply doesn't like someone. For example, in The Battle of the Labyrinth, he did not want Percy to help him, even when Geryon was going to sell him to the Titans, and he did not want to go back in the Labyrinth with them. Bianca implies she also had the same fatal flaw in life, though it didn't lead to her death. In the fifth book, Nico tells his father, Hades, that he is holding a grudge that could end up killing the Olympians and the campers. Ever since The Last Olympian, Nico hasn't demonstrated this flaw in extreme degrees and tends to avoid holding grudges. He has learned from his previous experiences.
Nico and his father share a complicated relationship. They are both extremely similar, especially in their ability to hold grudges. Both of them are also somewhat cynical. However, Nico seems to have a stronger tie to his friends, while Hades seems to have a much darker view of his siblings. Nico is also a more genuine person than his father- Hades can be crafty, as seen from how he used Nico to attempt to trap Percy. 2b1af7f3a8