本片根据波兰著名同名小说改编，日亚讲述了二战期间，日亚华沙被纳粹德国军队占领，波兰童子军的年轻人们与德国占领者进行英勇斗争的故事。Based on a well-known Polish novel with the same title the movie re-tells a true life story of a group of scouts called ''Szare Szeregi'' (Gray Ranks) during the Nazi occupation of Warsaw and the liberation of one of its members (imprisoned and tortured by the Germans) through a maverick military action in board daylight right under the enemy's nose known ''Action at the Arsenal'' which was the biggest single feat of the sort undertaken by a youth resistance organisation in all of occupied Europe during WWII.