Q & Q - Season 1 (1974)

Q & Q investigate 'the old mill' where the Bennebroeck family resides. Staying with them is the scary man, Axel Zaneck, who in turn visits I.Q to ask questions about the boys. When Eduard Bennebroeck goes to pay off the local landowner Zwartjes, Aristides takes a closer look at the old mill. But then Eduard's sister Berthe returns home. Aristides quickly invents a story about looking to by some cuff links for his grandfather.

Grandpa wants to buy the Old Mill. But Farner Zwartjes gets greedy after receiving a cash offer from current resident Ed Bennebroeck and raises his price. Aristides has seen a portrait of the missing Van Slingelandt at the Bennebroeck place. Grandpa visits Van Slingelandt's landlady and finds himself being shadowed by a man in a white raincoat.

The boys are shocked to find Zaneck on the Quarles van Ispen doorstep. Farmer Zwartjes is hospitalized after getting hit on the head with a wooden plank in his own barn. Local Builder Pies is slowly converting the Quant attic into a darkroom for Wilbur and wants his son André to show his drawings to I.Q.

Berthe and Eduard Bennebroeck are dismayed to learn that some children have been asking questions about the medicine they requested at the drugstore. Wilbur and Aristide's fathers finally meet each other and Juultje tries to cheer up shy André. The investigating Q's find Van Slingelandt's car parked at the Hotel Schoon Runkum. But soon afterward Zaneck picks up the Citroën and has it demolished.

Grandpa and Aristides' father Charles have found evidence that Zwartjes was hit on the head instead of having a mere accident. They also found a cigarette at the scene of the crime that turns out to be from a Sulleila packet. The three Q-kids try to recreate the circumstances of the fateful photograph when they are interrupted by Zaneck.

Juultje learns from André that Bennebroeck is proficient at making tiny technical gadgets. For instance he helped André make a pair of walkie talkies for him and his father. Grandpa spots the man with the white raincoat who's been following him at the Runkum hotel.

During the garden party at the Quarles van Ispen house, Aristides and Wilbur borrow the Pies' walkie talkies and head over to Bennebroeck's old mill. However, Zaneck also aims to take advantage of the busy household and search for the ring in Aristides' room.

Van Slingelandt's parents come to Grandpa with their concerns for Anthony Jr. Aristides has been caught by Zaneck, who has also found the picture that started it all, if not the ring.

Now both Q boys have been captured by Zaneck and the Bennebroecks. Berthe cannot stand taking care of the increasingly ill (yet still clinging on to life) Anthony van Slingelandt. She calls Charles Quarles van Ispen, the surgeon about his son and forces him to take a look at Anthony.

The plot begins to unravel as André and Juultje have figured out the purpose of the all important ring and the man in the white raincoat closes in on Alex Zaneck. Meanwhile, both the Q boys and Aristides father Charles find themselves unable to leave the Bennebroeck household.