As always, Sickan has come up with a new plan. This time he wants to rob the IKEA furniture store. During their nightly break-in Sickan discovers that the store is used as a secret smuggling central for sending American computers to the Soviet Union. The computers are picked up by Soviet submarines sneaking into the Swedish archipelago. Naturally, it is their arch enemy Wall-Enberg who is behind all of this.

Vanheden and Dynamite-Harry are approached by Sickan's grandmother and Sickan's younger brother Sven-Ingvar. Their evil nemesis Wall-Enberg are planning to steal billions of euros of the European Union's grants to culture. The grant of 350 million kronor, paid by an Italian bank acting as intermediary, equals 60 billion lire but through assistance of a Sicilian "businessman", this sum becomes 60 billion kronor when transferred. The money is to be transferred to a large number of bank accounts, and the account numbers are saved on a floppy disc that the Jönsson gang is trying to steal.

Vanheden and Dynamit-Harry, together with Harry's fiancée Doris, are in Mallorca while Sickan is still in Stockholm. However, Wall-Enberg talks him into doing a break-in at Las Palmas cathedral in Mallorca. Once persuaded, he can't resist the temptation and travels to Mallorca as well. However, Wall-Enberg obviously can't be trusted. Sickan is framed, caught and put in jail. While being escorted home to Sweden again, Vanheden and Harry sets up a plan to break him free. Sickan, once free, wants payback. The gang discover that an antiques dealer called Germann has something to do with the whole thing and that she's also collaborating with Wall-Enberg. The gang then decide to take a closer look at her and her antiques and they discover that there's a heist being planned against the cathedral in Palma.

Sickan has a new plan. This time, the gang are going to steal a small computer micro chip which contains a top secret plan of what the government intends to do with Sweden in the future. But, Wall-Enberg is also planning to steal the chip. The payment will be 55 million Swedish crowns in gold and diamonds to whoever can deliver the chip to the foreign investors. Who will grab hold of the chip, the Jönsson gang or Wall-Enberg?

The movie begins with the Jönsson gang making a minor burglary. It goes wrong and the gang leader, Sickan, gets caught. After he has spent 10 months in jail, Vanheden and Rocky come to welcome him when he's released. But he doesn't take notice of them, and he's picked up by the mysterious banker Wall-Enberg Jr. instead. He wants Sickan to perform a burglary in Switzerland, in order to retrieve the famous Bedford Diamonds. Sickan does this but is fooled by Wall-Enberg and nearly gets caught. When he returns to Sweden and re-unites with his old gang members, he's set on revenge, both physically and psychologically...

Sickan, Vanheden and Rocky try to rob the Berns nightclub one night, but Vanheden has made the mistake to invite his constantly drunk cousin, the old dynamiter Dynamite-Harry and he ruins the plan. Sickan is arrested, and has to spend 10 months in a small, locked room. When he is released, he has a new plan, but Rocky and Vanheden have decided to go straight. Together with Dynamite-Harry, Sickan plans to rob a cold store, managed by their arch-enemy, Wall-Enberg.

Sickan, the leader of the criminal Jönsson gang is incarcerated in a mental institution, attended by Dr M.A. Busé, who admire a handbook in crime that Sickan has been writing. Blackmailed by the nefarious banker Wall-Enberg, Dr Busé and Sickan's partners Vanheden and Dynamite-Harry execute Sickan's plan of stealing the valuable Black Diamond of the Romanovs from the National Museum.

When Vanheden and Dynamit-Harry tries to break doctor Busé out of jail, they get Herman Melvin instead. He has been working at the Swedish Mint and the doctor, who has started to think like Sickan, has written a plan for making a burglary there, on Melvin's back. However, something goes wrong. They don't get a lot of Deutsch-marks as they planned but instead, they end up on a ship going to Poland, together with bunches and bunches of Polish Zlotys (the Polish currency). In Poland, they discover that the mafia are very interested in that money and Wall-Enberg is working with the mafia.

Vanheden and Dynamite-Harry are approached by Sickan's grandmother and Sickan's younger brother Sven-Ingvar. Their evil nemesis Wall-Enberg are planning to steal billions of euros of the European Union's grants to culture. The grant of 350 million kronor, paid by an Italian bank acting as intermediary, equals 60 billion lire but through assistance of a Sicilian "businessman", this sum becomes 60 billion kronor when transferred. The money is to be transferred to a large number of bank accounts, and the account numbers are saved on a floppy disc that the Jönsson gang is trying to steal.