The plot begins exactly at the end of the second episode. Ezio returns to Montergiorni, to the Auditore family villa. However, it is soon occupied and destroyed by Cesare Borgia, son of Rodrigo Borgia (the main negative character of Assassin's Creed II). Cesare kills Ezio's uncle Mario, giving Ezio another reason to seek revenge and fight the Templars. In the present day, Desmond Miles, along with Lucy Stillman, Shaun and Rebecca have set up a base and hideout from the Templars in Villa Auditore, it is from here that Desmond joins Animo. Ezio escapes from the villa to Rome, where he is later reunited with his mother and sister Claudia. Having left most of his equipment at Villa Montergiorni, he has to rebuild his respect, which is helped in Rome mainly by Niccolo Machiavelli, who is Ezio's mentor. In addition, Ezio builds up his brotherhood of Assassins, meaning that he can call on the help of friendly Assassins or send Assassins out on their own on various missions. Ezio can also rid Rome of the influence of the Borgias during the course of the game, building shops or buying up monuments to make money and strengthen his influence. Again, the entire plot revolves around the "Piece of Eden" object, which was stolen early in the game by Cesare Borgia, who gave it to his father. Ezio has to build up respect and increase the influence of the Assassins in Rome, restoring the thieves' and mercenaries' guilds as well as the brothel (run by Claudia and her mother). Machiavelli is a powerful Assassin and Ezio's mentor. The leader of the thieves' guild, La Volpe, suspects Machiavelli of informing on the Borgias, but his suspicions are not based on truth, as Ezio later discovers. Ezio's sister Claudia later becomes an assassin as well. Machiavelli's spies discover the whereabouts of Cesare Borgia, making the situation more than suitable for his elimination. In the Castle of the Angels, Ezio watches as Pope Rodrigo Borgia poisons his son Cesare with a poisoned apple because it threatens his own influence. Cesare ends up murdering his father himself, wanting the Apple (a piece of Paradise) for himself, but his sister, Lucrezia Borgia, will not tell her brother where the Apple is and Cesare's lust for power ends their incestuous love affair, much to Lucrezia's chagrin. Ezio stalks Cesare, and Lucrezia even helps Ezio a little. Ezio eventually takes possession of the Apple and, through its power, finally destroys Cesare's army and kills Cesare Borgia himself. Eventually, he safely keeps the Apple in hiding because it is too powerful and Ezio fears it might be misused. In the present day, Desmod and his friends discover Ezio's hiding place and retrieve the Apple, which has been stored in a crypt beneath the Colosseum. A hologram of Minerva appears to Desmond, claiming that the apocalypse is the only possible way to purify humanity and save it from itself. At the end, Desmond, under the influence of the Apple, stabs Lucy in the stomach with a hidden blade, killing her.
Source: https://cs.wikipedia.org/wiki/Assassin%27s_Creed:_Brotherhood
"I will go into the black heart of the realm to root out my enemies. But Rome was not built in a day, and it will not be rebuilt by a lone Assassin. I am Ezio Auditore da Firenze. And this is my brotherhood." All that's left of the once mighty Rome are ruins. Suffering and disgrace rule the city, and its inhabitants live in the shadow of the ruthless Borgia family. Only one man can free the people from the tyranny of the Borgias - Ezio Auditore, the master assassin. Ezio's campaign takes him to the limits of his abilities. Cesare Borgia, more insidious and dangerous than his father the Pope, will not rest until he has conquered Italy. And in treacherous times, conspirators can be found everywhere, even in the ranks of the Brotherhood itself...
Source: http://www.databazeknih.cz/knihy/assassins-creed-bratrstvo-63907
