When something bad happens at Aunt Til's exposition, the Sinterklaas fest seems to end once and for all. A series of terrible events is set in motion, which treatens to free the evil Dr. Brein and her accomplices.
The story of Operation Market Garden—a failed attempt by the allies in the latter stages of WWII to end the war quickly by securing three bridges in Holland allowing access over the Rhine into Germany. A combination of poor allied intelligence and the presence of two crack German panzer divisions meant that the final part of this operation (the bridge in Arnhem over the Rhine) was doomed to failure.
In the late 19th century, a young woman moves to Amsterdam with her family and tries to make a living. Preyed upon by various men, she nonetheless rises in society.
A group of covert CIA operatives trailing a potential new energy source are double-crossed by corrupt agent Morgan, who causes a helicopter crash in remote South Africa. The sole survivor, suffering severe amnesia, is nursed to recovery by a kindly native tribe who call him "Whoami" after the question he keeps asking. With the help of a mysterious reporter Christine, Whoami pieces together his past and tracks the turncoat agent and his criminal cohorts.
The Baron and his cronies steal a precious crown and hide in a secret room of an abandoned castle. With the help of their tiny robot Robin, Bassie and Adriaan set out to find the crown and return it to the museum.
The mayor of Sunny Dale see a chance to get rid of the Flodder family: They send the asocial bunch for an international exchange to New York. There they get confused with a Russian delegation of medical doctors while the street worker Werner who accompanies them becomes imprisoned.
Professor Archibald Chagrijn exposes the world to his blubbering gas, which makes people sad and causes them to cry. Bassie proves immune to the blubbering gas -- as he has had an overdose of laughing gas. The professor is hiding on the Canary Islands, but Bassie and Adriaan manage to track him down.
The Baron, B2 and Vlugge Japie have been in prison since the previous adventure. Now that they have escaped, they want to take revenge on Bassie and Adriaan. They steal a valuable crown from a museum after escaping from prison. They hide in a secret room of an abandoned castle. The crooks want a large amount of ransom for the crown, otherwise they will have it melted down, and they then lure Bassie and Adriaan into a trap. However, the duo escapes. But then it turns out that the baron accuses them of stealing the ransom. So they have to find the crooks to prove their innocence. With the help of a computer program made by Robin, they find the hiding place. The crooks try to flee abroad, but on the way they drive their car into a trap that Bassie and Adriaan have set up. They are driven to the police, where they are immediately put behind bars.