It's wartime. Gus and Lars, two enemy lieutenants in search of victory, find themselves in an abandoned music school. Both are locked in a classroom full of musical instruments. Only a wall separates the two soldiers. The attacks are fierce. When Gus runs out of ammunition, he taunts his enemy by banging on the snare drum on the wall. Lars retaliates with a trombone, making an unpleasant noise. A melody emerges as the exchange of sounds continues. The duel gradually turns into a duet...