Fayson's dream of becoming a detective finally comes true when her cousins recruit her to their top-secret gang. But the Greatest Gang of All Time isn't exactly living up to their name, constantly side-tracked by food, sleep and squabbles. Determined to set things right, Fayson takes charges and dives into the mystery surrounding a mysterious shadow haunting the island's lighthouse. 

With tensions rising within the gang, Fayson relies on her sharp smarts and inspiration from her favourite mystery novels to crack the case. Can she unravel the secrets, confront the shadow, and unite her friends?