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 planned marriage between Premierpiet and Probleempiet is in jeopardy, scholars Hans and Frans Steenstra have been kidnapped, and a rare ruby has been stolen from the Rijksmuseum. The dangerous Dr. Brein is behind all of this. Sinterklaas must intervene and even sends his Pieten on a trip to Switzerland to prevent Dr. Brein's criminal organization from gaining power.