A young cat named Vincent, in the company of Maurice the mouse, escapes from the flood in an old harpsichord, which is picked up by sailors and sent to St. Petersburg, where it ends up in the Hermitage. There, Vincent meets an elite feline squad that has been protecting artwork from mice and other pests for centuries. Vincent dreams of finding a real cat family, but does not want to lose his friend Maurice, who saved his life. Vincent has to hide a friend, who also has one "little weakness" - Maurice loves to gnaw on masterpieces of painting. The situation becomes even more complicated when one of the greatest paintings of mankind, the Mona Lisa, arrives in the Hermitage, and it is the dream of all mice to gnaw it. But neither Vincent, nor Maurice, nor the cats of the Hermitage suspect that the painting is going to be stolen. And now Vincent will have to show all his resourcefulness and courage in order to save the masterpiece, protect the honor of the museum and win the love of a cat named Cleopatra from the Egyptian hall.