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.