During a summer stay with their uncle on a secluded island, young siblings Andy and Mark uncover that their quirky grandfather once owned the island but mysteriously disappeared, taking with him the key to a hidden fortune. As they explore the island’s enigmatic history, the brothers find out that their grandfather had created an intricate treasure hunt, one that promises immense wealth and the potential to mend their fractured family—if they can solve it in time. However, they are not alone in their pursuit; dark forces are also on the trail of the treasure and will stop at nothing to thwart the boys’ mission. As their adventure progresses, the brothers come to realize that the true treasure lies in the strength of family ties, and that some family secrets are destined to resurface.