So at the age of three, Oskar decides to stop growing but he doesn't want to spend his life going to doctors who'll try to figure out why.
He's walking around the house one day and realizes that the trapdoor to his family's basement is open. He quickly hatches a plan to throw himself down the basement steps.
He thinks this will give the grownups a reason for his failure to grow.
Later, he feels himself being carried into the living room by his father's friend Greff. He can remember his mother slapping at his father's face and calling him a murderer, since it was Alfred who left the trapdoor to the basement open.
His mother never forgave his father for forgetting about the door.
So now that he's stopped growing, Oskar decides that he needs to play his drum constantly as a way of distancing himself from the world of adults. He drums incessantly.
As you can imagine, sometimes adults find his drumming annoying and try to take his drum away. So how did Oskar defend himself?
Turns out that he has a weird, high pitched voice that shatters glass whenever he screams. And he doesn't hesitate to use it if someone takes his drum.
Again, we're called upon to ask how sane the guy telling this story actually is.
Growing up, Oskar didn't play much with the neighborhood kids.
Whenever he'd pass them with his drum, they'd tease him about his glass-shattering voice.
His ability to shatter glass proves to be a problem to Oskar, though, since every single broken window in his neighborhood gets blamed on him.
Oskar tells the story of the first time he ever unleashed his shattering scream.
It happened one day only a few weeks after his third birthday. He was walking around playing his drum, which had a hole punched into its tin. Seems these tin drums wear out really quickly.
Oskar's father Alfred is extra careful since Oskar's fall down the stairs, so he tries to take the drum away because he's afraid Oskar will cut his hands on the tin.
When he takes the drum away, Oskar lets out a scream that shatters a bunch of glasses in the family home.
Alfred gets mad and tries to hit him, but this only results in more shattered glass.
From this point forward adults realize they won't be able to physically force Oskar to do anything he doesn't want to do. He's the child, but they're helpless.
After he shatters all the light bulbs in the room, the lights go out. When Oskar's grandmother brings in candles to relight the room, she finds that the whole crowd of adults is involved in some sort of orgy. At least that's how Oskar tells it.
Once things have calmed down and the room is relit, Oskar's mother, father, and Uncle Jan sit down to play a game of skat.
Oskar hides underneath the table while the adults are playing. He notices during the game that his uncle Jan has slipped his shoe off and is pressing his foot into his (Oskar's) mother's groin. So yeah, there's definitely still something going on between the two of them.
The next person who tries to take Oskar's drum is Oskar's family doctor, Dr. Hollatz. During a routine checkup, Hollatz explains to Oskar's mother once again that Oskar won't grow anymore. Then he tries to take Oskar's drum, and Oskar lets out a scream that shatters all the jars full of specimens in Dr. Hollatz's office.
Dr. Hollatz takes it pretty well. He writes an article about Oskar's unique voice that gets published in a well-known medical journal.
Back in the asylum, Oskar sadly mentions that his voice doesn't have the power to shatter glass anymore.