The Olsen Gang’s Last Trick

After 17 years in the Institute for Theoretical Crime, Egon leaves to participate in a television talk show. Benny and Kjeld, who see the broadcast, decide to seek him out at once. The reunion sets in motion a refreshed plan to pull off a major caper.

Egon, needing a toilet after the show, exits the studio and meets Benny. They decide to visit Kjeld at the nursing home to reconnect and plot. Kjeld reveals he has met Ruth, who wants to buy an apartment in Málaga, shaping a new capital plan.

Across his time in psychiatry, Egon has devised many schemes and now reveals a plan to lead the Olsen gang to the necessary capital by stealing the English crown jewels. The Wandenberg documents and the safe become central leverage. The plan ties personal motives to a larger political threat.

Department head Hallandsen recognizes Egon from the broadcast, realizing that the Wandenberg documents must be kept secret. He orders Holm-Hansen to find Egon. He also recalls the Franz Jäger safe as the potential key to locating him.

Holm-Hansen consults detective assistant Jensen, who insists on checking the Franz Jäger safe from 1944, the only one left in Denmark. The safe is located in the Department of Theoretical Crime and is a potential trap for Egon. The pursuit accelerates as the safe becomes central to the chase.

At the institute, Egon plans to steal his own plans from the safe, hoping to use them for leverage. The headmaster tries to lock him up again as a precaution. Holm-Hansen intervenes and escorts Egon out, allowing Kjeld and Benny to slip away unnoticed.

Egon is brought before Hallandsen, who assigns him to steal the Wandenberg documents for a measured reward. Two ministry officers assist his operation, and Egon quickly secures the documents from the ministry archive. The assignment intensifies the stake in the ongoing chase.

After Hallandsen obtains the documents, Egon demands his reward but is locked up in a dungeon. Kjeld and Benny manage a daring rescue at the last moment, freeing Egon. The trio prepares to turn the tables on their pursuers.

Hallandsen intends to destroy the Wandenberg documents at a state destruction facility, but Egon plans to prevent this to keep the leverage. He aims to bring the suitcase into his possession to blackmail Hallandsen. The confrontation heightens as the stakes rise.

Together with Benny and Kjeld, Egon uses a boat hook, washing-up liquid, and other improvised tools to reclaim the suitcase with the Wandenberg documents. They succeed in taking back what they need and avoiding total loss. Hallandsen's scheme begins to falter.

On the road to deliver the documents, Ruth ends up in Kjeld's seat, insisting that he is not well; Egon reluctantly allows her to accompany. The group proceeds toward the Øresund construction site with the package in hand. Tension rises as alliance shifts occur.

Bøffen and Alf ambush the group and push them into a construction cave. There, they must work with Ruth and the others to extricate themselves, while Egon tries to salvage the documents and his plans. The peril peaks as the escape seems uncertain.

Kjeld's son Børge, now an international manager, returns to Denmark after hearing what happened. He seeks out Egon, Benny, and Ruth and encounters them at the construction site. His arrival adds a new dynamic to the group’s fragile alliance.

Benny bids farewell as Egon pushes for his reward, but Ruth and Alf throw the suitcases containing Egon's plans and the Wandenberg documents onto a construction machine and disappear. The documents seem to vanish, threatening to undermine all of Egon's schemes.

The remaining Olsen gang members travel to Børge's villa in Portugal to live in peace. Egon still harbors the plan to steal the crown jewels, hinting at a final caper beyond the film’s end. The group's future remains uncertain, even in exile.