Follow the adventures of Fievel Mousekewitz, a Russian-Jewish mouse immigrant to the United States in 1885.
While emigrating to the United States, a young Russian mouse gets separated from his family and must relocate them while trying to survive in a new country.
A few years after immigrating to the United States in 1885, in the year 1890, the impoverished Mousekewitz family discovers that conditions are not as ideal as they had hoped, as they find themselves still struggling against the attacks of mouse-hungry cats. Fievel spends his days thinking about the Wild West dog-sheriff Wylie Burp, while his older sister, Tanya, dreams of becoming a singer. Meanwhile, Tiger's girlfriend, Miss Kitty, leaves him to find a new life out west, remarking that perhaps she is looking for "a cat that's more like a dog."
In the historic melting pot of 19th century New York City, Fievel and the Mousekewitz family are struggling to make their American dream come true. But when a mysterious treasure map leads Fievel and his friends to a secret world of Native American mice living beneath the city, he finds something even more precious than gold and jewels!
After the events of the third film (1885-1910), but before the second (1890-1900), in the year 1910 or 1915, Fievel, his friend Tony, and his sister Tanya Child labour at the local newspaper, where the audience is introduced to Nellie, who wants to be an important reporter, but only gets small assignments, as if she were a secretary to Reed, the newspaper's editor. Throughout the film, Tanya tries to win Reed's heart, while Tony tries to get noticed by Reed and promoted to a reporter. As in the previous movies, where a mouse installation is directly below its human installation counterpart, the newspaper offices the mice work in is directly underneath the newspaper offices the humans work in.