Two down and out brothers are left a failing string company and an old house with unknown historical significance. Lars (Lee Evans) wants to keep the company in their fathers memory, but Ernie (Nathan Lane) wants to sale it all. When Ernie inadvertently kills the mayor in his famous restaurant he changes his tune. The two brothers move into the run down mansion, and quickly discover blue prints that show the house has a famous background. They call the house the missing LaRue. They are determined to remodel the house, and sale it to keep the family business from going under. There is only one little problem. A mouse lives in the house, and is determined to stop any construction from being completed. The time is running out for the brothers to fix up the mansion, as they owe a mortgage of a whopping $1200, and it is due in two days.
The brothers bring in a monster cat, and crazed exterminator but neither are able to destroy the clever little mouse. The exterminator goes insane due to the fact he is unable to destroy such a little rodent. In the end the house is all but destroyed, and the brothers must return to the factory, for they have no where else to go. Not realizing the mouse has hitched a ride to the factory, the brothers lament on how to continue on.
The ingenious little mouse manages to drop a wheel of cheese into the wax machine, and the string machine is turned on. The brothers see that there is a future with the mouse, and his invention of string cheese. They decide to become a team with the mouse, and invent new flavors of exotic string cheeses. The mouse will help them as a spokesperson, and taste tester.
The picture of their father in the beginning shows a frowning old man. In the end the picture is altered with a smile on his face.