It is the fire brigade's day in Valleby, but in the middle of the gathering in the town square the alarm sounds. It's burning in Muhammed Karat's gold shop! Almost at the same time, the alarm goes off at the museum. The fires are small and are extinguished quickly, but several objects have disappeared.

Counterfeit banknotes are being spread in Valleby. At the same time, it's discovered that someone has used the school's new color copier. Can there be a connection? Lasse and Maja start an investigation, but time is short if they are to solve the case before school ends.

There is a fashion fever in Valleby when the city's best dressed residents are to be crowned. Fashion guru Jean-Pierre is the guest judge, but when his life partner, the cat Lulu, disappears, he loses the spark and the competition is in danger. At the same time, Jean-Pierre receives a nasty threatening letter.

Valleby's priest will retire during a grand ceremony, when the bishop's silver crosier disappears. Lasse and Maja realize that they have to stay in the church during the night and scout, but the thief is cunning and the suspects are many.

Several patients have lost their jewelery while they were in the hospital and plastered, but no one can be arrested as long as the stolen jewelery isn't found. Lasse and Maja sets a trap to help the police chief catch the thief and solve the mystery.

It's time for the Valleby Day. In the middle of an award ceremony, the stage collapses and an expensive necklace disappears, along with the money raised for "Världens Barn" charity. Can Lasse and Maja solve the mystery before the thief leaves the city?