A year has passed since Basil's battle with Ratigan atop Big Ben, and the Flavershams have moved to the American West to put that horror behind them. However, once arriving in Green River, Olivia's father is kidnapped once again. Can Olivia hone her detective skills to find him? Luckily, she'll get a little help from one Fievel Mousekewitz, setting the two of them off on a journey that will include many old friends and foes alike.
Little do the two of them know that Ratigan survived the fall from Big Ben, and has teamed up with Cat R. Waul in a scheme to take control of Green River, and eventually, the United States.
The story takes place four years after Basil's American Tail, in 1890. This creates an alternate timeline in which the events of The Great Mouse Detective were moved back eight years to 1889.
- Olivia Flaversham - (The main protagonist) An inquisitive young girl who wants to be a detective, and loves her father very much.
- Hiram Flaversham - Olivia's father, a toy maker by trade, who wants to open a toy shop in Green River.
- Fievel Mousekewitz - (The dueteragonist) An outgoing, courageous boy who likes to fashion himself as a hero.
- Tanya Mousekewitz - (The tritagonist) Fievel's big sister, who's dream is to become a famous singer.
- The Mousekewitz family- Papa, Mama and Fievel's little sister Yasha.
- Tiger - (The secondary tritagonist) A big orange cat, and Fievel's best friend. He is trying to lose weight for his girlfriend.
- Miss Kitty - A barroom singer who manages the saloon in Green River.
- Tony and Bridget Toponi - Fievel's friends who helped him when he lost his family in New York. Tony is now a bartender while Bridget is a political activist. They are now married and have a daughter named Aisling.
- Nellie Brie - The star reporter of the Daily Nibbler, who is officially in Green River to write an article about its New York migrants, but has another article in mind.
- Basil of Baker Street - The Great Mouse Detective, still residing in London.
- Vartan Mookian - (original character) Nellie Brie's new assistant, an immigrant from the Ottoman Empire who loves drawing in his sketchbook. He speaks little English.
- Ratigan - (The main antagonist) The Napoleon of Crime, a notorious criminal who is relocating from England to America.
- Cat R. Waul - (The other main antagonist) A classy British cat who's schemes tend to involve mice becoming mouseburgers.
- Fidget - (The secondary antagonist) A peg-legged bat who is somewhat reluctantly still serving his abusive boss Ratigan.
- Chula - (The other secondary antagonist) A tarantula and loyal follower of Cat R. Waul.
The sequel to Basil's American Tail was first posted on Deviant Art May 21, 2012, and on Fanficion.net the following December. A much longer story than the first, it took most of the rest of the year to complete. It can be read here or here.
Reasons for having the story take place in 1890 come from a variety of factors. Basil and Nellie would have been apart for eleven years otherwise, and the author wanted Fievel and Olivia to remain close in age. The story takes place two years after the events of An American Tail: Fievel Goes West, and assumes the events of the direct-to-video An American Tail sequels took place in 1887. Meanwhile the events in The Great Mouse Detective take place just as they did in the film, but eight years earlier.
Though not the first original character in the fan fiction series, Vartan Mookian was the first prominent one. The author did not want the character to take too much prominence in the story, as often happens in fan fiction, so he is a secondary character. Vartan is an Armenian immigrant from the Ottoman Empire, which in the AAT universe is ruled by Turkish cats. His name is derived from the Armenian word for mouse, "mook", and ends in "ian" like most Armenian names do. The human equivalent would be "Manookian", much as Moskowitz is for Mousekewitz.
Like it's predecessor, this story was also called into question by Fanfiction.net's moderators for copyright infringement in December 2013. However unlike the first story, which needed to have entire scenes cut for it to remain on the site, this story only needed a little cleaning up, and remains largely unchanged, due to the fact that it is not directly based on a movie, rather it is a whole new story.
Its sequel, The Great Mouse Reporter, takes place a few months after this story. It is currently still in production, and available on both websites as the other two. This one is the longest story of the series thus far and has taken the longest to complete. It is unknown (even by the author) if there will be a fourth story in this series or not.