The story takes place in the far future of the 50th Century A.D.

While visiting Luna for the festival, Viscount Albert de Morcerf and Baron Franz d'Epinay make the acquaintance of the Count of Monte Cristo, a self-made nobleman. When they part, the Count promises to visit Albert in Paris. After he arrives, he introduces himself to the most powerful families in France (the Morcerfs, the Danglars, and the Villeforts).

The general plot of Gankutsuou, while broadly the same as the novel on which it is based, changes many aspects of the source material. Whereas Alexandre Dumas's original novel is focused heavily on the Count, Gankutsuou's narrative places more importance on the character of Albert and his friends and their inter-relationships. In the novel, the events in the Count's life proceed chronologically; in the anime, the story begins with Albert and Franz meeting the Count on Luna (which occurs many hundreds of pages into the book, in Rome), and the back story is pieced together throughout the series. The plot changes include supernatural elements, different fates for some characters, the disposal of several side-plots, and an altogether different ending.

These changes result in a different tone; in the novel the Count's quest for revenge is seen very sympathetically, but various plot elements in the anime lead the viewer's sympathy towards Albert, making the Count a far more antagonizing figure. Gankutsuou's plot could largely be classified as a coming-of-age story for Albert, catalyzed by the discovery of the dark history of the Count.
(source: Wikipedia)