Following the Olsen Gang's only successful robbery in the previous film, they are seemingly living the perfect life in the bathing sun in Mallorca. Particularly Yvonne, who has turned into an alcoholic. But they are not happy, as the suitcase containing their money is always chained to Egon. Unfortunately, Bøffen has tracked them down, and he manages to steal all their money. Egon ends up in prison back in Denmark, which gives the rest of the gang a good reason to go home too. When Egon gets out of prison, he's got a new plan, as usual. So has Yvonne, however, she has alerted the police about the money which were stolen from them in Spain, and she asks for an advance in return. Egon also wants their money back, but it will be complicated. The money has now been invested in gold bars, which have to shipped by train - in an armored Franz Jäger wagon. Everything is seemingly in control for Egon. However, he has overseen that the railway company has changed the schedule to summertime, rendering his plan worthless and it results in a dangerous task for the gang. Meanwhile, the police have arranged a summer outing at the railway company and Bøffen have discovered their business. The gang are actually successful in stealing the gold bars and they buy the majority stake in a Norway company. However, the tax administration do not see the income from Egon's trade appearing in the accounts, and so he ends up behind bars again.