In pre-Nazi Germany, Alexander wants to win a painting contest at all costs, to make an impression on Lotte, the classmate he has a crush on. The two kids spend their afternoons with friends, including Maulwurf, an inventor. His latest invention is a color based on mother-of-pearl. Alexander steals it and Gruber, a rancorous boy disliked by many, discovers the truth and tries to turn the situation to his advantage. Accusing the students in another class of the theft, he tries to become a leader in the conflict that’s arising. Alexander, prisoner in a web of lies, is increasingly estranged from his friends.
