The tween, Mads, finds it hard to fit in. Having feelings for a girl in class and a clumsy farther who is a teacher at his school doesn't help. By an unforeseen chance of events, Mads becomes somewhat of a hero, but will he win the girl?

Everything is normal with the Krumborg family – but when you know them, nothing can surprise you anymore. The two robbers Boris and Ivan want to kidnap Krumme. Krumme wants to learn to ride a horse. Mom wants a healthy Christmas. Dad doesn't want a healthy Christmas. And it's hardly surprising that Krumme's Christmas present for Yrsa ends up under Mrs. Olsen's bed, or that caretaker Svendsen tries to repair Mrs. Olsen's sink – even though it's not broken. And the youngest member of the family, Grunk, has eaten all the Christmas decorations. Yes, everything is completely normal in the Krumborg family...

The Krunborg family has new problems: a freshly painted house that won't dry, a tent with holes and a car that won't go anywhere and much much more.

Krumme argues with his whole class about whether Santa Claus exists. Up at Santa's house, the magic book has disappeared, and that means the end of Christmas. So now Krumme has to prove that Santa Claus exists and save Christmas. But the robbers Boris and Ivan are also on the hunt for Santa's book. All in all, a perfectly normal Christmas at the Krummer family's house.

Mads "Crumb" Krumborg need a new bike so he can take part in an important race against a neighboring school. But it will be difficult to afford to buy a new printer, since the boy's father suddenly decides to terminate his job to invent a machine that according to him will change the world. At the same time a couple of crooks wind of his father's invention, and when the family Krum Borg's future is in problems, Crumb and his siblings to the occasion and save the day.

The screen takes up a lot of space in the Krumborg family's everyday life. Mom thinks the family should get closer, so Krumme suggests a screen-free week, because that way Krumme can get rid of his old crappy cell phone. Mom thinks it's a good idea, Dad does what Mom says, and Grunk just plans to cheat. But what are they supposed to do? Krumme finds some old Kim books in the attic, which he devours, and he is inspired to start his own detective agency with his friend Tom. When the criminals, Tina and Jeff, steal the Anastasia diamond from the National Museum, Krumme sees his chance: to catch the criminals and win Yrsa's heart. But it's not as easy as in the Kim books, because it's hard to be 11 years old when you also want to win Yrsa's love.