A candidate in a game show is hunted by three men. He will get a Million DMark, if he survives for a week; the hunters will get the money, if they can kill the candidate. The audience of the show is watching the transmissions of twenty camera teams filming the hunt. The showmaster appeals to the TV-viewers to help either the candidate or the hunters, whomever they want.

The four young snoopers Tim, Karl, Kloesschen and Gaby by chance discover a hidden cave near an old castle. In it there's a board that seems to describe the way to a legendary sword. They ask their history teacher Schindler about it. He forbids them further actions, but secretly continues investigations with help of two ruthless criminals. But our young heros don't give up on an adventure so fast...

While King Louis X of France is on a campaign, Queen Marguerite is reigning in Paris. During this time, the inhabitants of the city are disturbed by mysterious murders near a tower.