The work consists of a banner displayed on a horse-chestnut tree located at the park in front of the CCA Ujazdowski Castle. The tree communicates with the exhibition space through a print that shows a letter sent to Sophie Liebknecht by Rosa Luxemburg from prison in Wroclaw in 1917. The letter makes an account of a flock of crows passing and chatting among themselves up in the sky, above the prison yard where Rosa was among other prisoners. Rosa Luxemburg uses the onomatopoeia "Kau-Kau" for depicting the sound of the crows. The tree and banner can be seen from the window adjacent to the place where the letter is exhibited.