A young boy and his dog, who happens to have a genius-level IQ, spring into action when their time-travel machine is stolen and moments in history begin to be changed.

A young mouse named Fievel and his family decide to migrate to America, a “land without cats,” at the turn of the 20th century. But somehow, Fievel ends up in the New World alone and must fend off not only the felines he never thought he’d have to deal with again but also the loneliness of being away from home.

A friendly troll with a magic green thumb grows one flower too many for the queen, whose laws require all trolls to be mean ugly and scare humans whenever possible. As a punishment, he is exiled to a world of concrete, where he should live a life of proper trolldom: Manhattan.

Fievel and his friend Tony Toponi find a map that they believe points to a treasure buried somewhere beneath Old New York, and the plucky rodent is determined to find it. However, what he discovers under the city is a tribe of Native American mice who were driven underground by prejudiced European immigrants.