The sophisticated thief of art Robert "Cuma" Cuminski is released on probation from the local prison by the corrupt Doctor Wiaderny to organize the theft of the famous Leonardo Da Vinci painting "Lady with Ermine" for the dealer Gruby. Three years ago, Cuma was accidentally arrested by the snoopy detective Wilk after a successful heist in the house of the collector Lehman, but he has not ratted his comrade Julian.