Plot
Set in between the third film (Late 1880s) and second film (1892), Fievel, his friend, Tony and his sister, Tanya all get jobs 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.
Like 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.
Nellie gets a chance when she is assigned to report mice who disappear overnight into holes that open up on their floor all over New York. Reed makes up a, as Nellie calls it, "so-called monster" that lives under Manhattan and takes mice away during the night to add more excitement to the otherwise unimportant story, intending to sell more papers.
The night monster creates fears among the readers, as could be expected. Fievel begins having nightmares that cause him to lose sleep because of his fear of the monster; the film opens up with Fievel having a dream about being chased by what he thinks the monster looks like.
When, through Tanya, he is assigned the job of following Nellie and drawing up interperatations of what the monster looks like based on witness testimony, this makes his insomnia all the worse.
A particularly suspicious miniature French poodle named Madame Mousey,