Joachim Mahlke is a teenage boy in Danzig, Germany, while the second World War is still something that exists only in the news and in rumours about heroic deeds of known and unknown people.  He just learned to swim and together with his friends he enjoys swimming to a partially submerged minesweeper, just a few hundred meters from the shore.  While his friends enjoy the sun and discuss the issues of life that are important for teenage boys, Mahlke dives into the ship to hunt for treasures: an old record-player, a label on a door, a screwdriver,...   They feature, hanging on a shoelace tied around his neck, until the next treasure comes up.

One day a war-hero comes to his school to speech about the glory of the war, and Mahlke steals his Iron Cross.  Though he is not suspected - except by his best friends - he reveals his act to the principal and is kicked out of school.  He always wanted to be a clown, his new school seems to be a one-way trip to the army, where it is now his turn to become a hero.  When he's on his first leave he visits his old friends, but somehow it's no longer the same as it used to be.  He doesn't want to return to the war...

The story is narrated by his close friend Pilenz, and one could almost say it is written down as it is spoken.  Certainly when he talks about what other people have said I recognize some of my friends ;-)  Throughout the story the narrator feels pretty guilty towards Mahlke; he repeatedly recalls an incident where a cat was sort of helped to see Mahlke's gian Adam's apple as a mouse.  Schoolboy-humor obviously, but later when the narrator starts to appreciate Mahlke he regrets that incident, yet never manages to say much about it.  And it's not so much this single incident it seems, but the fact that Mahlke was different, and perceived different, by his friends that later embarrasses Pilenz.

Because Mahlke is different.  He is not only blessed with a giant Adam's apple, but he is a Catholic and his name suggests a Polish origin, enough features to clearly separate him from the Germans.  And at the same time his friends admire him, he even is nicknamed "The Great Mahlke".  After all: he outperforms them every time.  By stealing the medal, by becoming the best swimmer even if he was the last one to learn it, by graduating the first, and by going to war while the others were still being trained.  Despite his dream of becoming a clown.  And in the war he lives up to his nickname, by destroying an impressive number of enemy tanks.  For this he earns his own medal.

And this ties the end of his story back to the beginning.  The story starts with the incident with the cat, where his Adam's apple was the mouse - and ends with a disappointing meeting with his former school-principal, where he is the mouse that is denied his speech by the cat-principal.  This forever shifts the balance in the relationship between Mahlke and the narrator.

This is many stories in one.  Teenage boys growing up.  Growing up in the National Socialist era in Eastern Germany.  An unresolved relationship between two friends.  An almost unreal atmosphere during the first part of the war.
The open ending of the story - what did happen to Mahlke? - leaves it up to you to decide which story you want to retain.