When their father died, brothers Ernie (Nathan Lane) and Lars (Lee Evans) inherited a thread factory and an old house. Lars was kicked out of the house by his snobbish wife because he refused to sell the thread factory, and the restaurant run by Ernie was suddenly hit by a disaster and was forced to live on the streets. The helpless brothers had to move to the old house left by their father. By chance, the two brothers learned that the old house they lived in was a masterpiece handed down by a master architect, which was of great artistic value and worth millions. The brothers decided to renovate the house and sell it, but found a mouse that lived in the house all year round. This clever mouse has developed feelings for the house and does not want the brothers to sell it, so around this old house, a battle between man and mouse is about to begin...