The twins, Zip and Zap, are sent to reeducation summer school. They form a gang with 3 others, opposing the school's tyranny with pranks. Later, they go treasure hunting.

Naughty twins Zip & Zap are punished and sent to summer school at Hope, a strict re-education center run by Falconetti, who rules with a heavy hand and an eyepatch and forbids all forms of recreation and entertainment. They form the Marble Gang, the children's Resistance, in order to defy the evil headmaster. Guided by intelligence, bravery and unbreakable faith in friendship, they uncover a mysterious secret hidden deep within the school and end up having the most exciting adventure of their lives.—Optis