Arthur is thrilled because tonight sees the end of the moon's 10th cycle and he will at last be able to return to the land of the Minimoys to reunite with Selenia. In the village, the Minimoys have prepared a huge banquet in his honor. But Arthur's father chooses this eagerly awaited day to announce he is cutting short their vacation at Granny's house. Then, as they are about to leave, a spider drops a grain of rice with a message as an S.O.S. engraved on it in Arthur's hand. There's no doubt about it, Selenia is in danger! Arthur doesn't think twice about flying to her rescue. Even if it means improvising a perilous passage, falling head first into Max's bar, bumping into the troops of Krob, the new tyrant of the Seven Kingdoms, saving Betameche's skin, fighting rats, frogs and hairy spiders.... Only to discover, when he arrives at the Minimoy village, that they never sent him a call for help! Who could possibly have laid such a cunning trap for our young hero?