Generał Nil is a Polish historical film, based on the life of general Emil August Fieldorf, pseudonym "Nil".

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.

Three Polish mathematicians are the first to crack the sophisticated Enigma code used by the Germans just before the Second World War. They build replicas of the Enigma machines and manage to get two of the machines to the British and French code-breakers before the German invasion of Poland in 1939; they ask that recognition be given to their work at the end of the war. After the invasion, the Polish cipher bureau escapes and continues their decoding in Algeria and unoccupied France.

The former head of the Institute of Science - Professor Molnar, returns to the Institute to seek treatment for his heart condition. The new director of the Institute, and his former assistant, Dr. Egberg had a falling out with Molnar after the latter considered his research unethical. However, after waking up from surgery, Molnar makes a horrifying discovery; Egberg has swapped their brains!

University student Anna and her boyfriend Tomek use a precious photograph to trace and unveil the complex wartime and post-war past of their parents.

As the Polish Army continues its march into Berlin corporal Naróg is tasked with delivering important documents to the staff headquarters.