When Basil the mouse detective sets out to discover if miniature cats really exist, danger appears at every turn as Basil gets closer to the mysterious miniature cats and their mouse king.
Basil leads an expedition up a towering Swiss mountain in search of a colony of mice who have been missing for centuries, but before he can solve the mystery he must confront a mysterious snow mouse and evil Professor Ratigan.
Basil, mouse and master detective seeking for the truth behind the theft of the Mousa Lisa, must also solve the mystery of his companion's disappearance.