In the early morning of 6 April 1941 in Belgrade, the capital of the Kingdom of Yugoslavia, two roguish ''bon vivants'' Petar Popara, nicknamed Crni (Blacky) and Marko Dren are heading home. They pass through Kalemegdan and shout salutes to Marko's brother Ivan who's an animal keeper in the Belgrade Zoo. Marko lets Blacky's pregnant wife Vera know that they enrolled Blacky in the Communist Party of Yugoslavia (KPJ).