Singapore's favourite sleuthing quartet returns in this third instalment of the series, set in the offshore Sisters' Islands. Su Lin, Su Yang, Bus, Zizi and their faithful parrot, Kuning, are camping on Big Sister's Island, one half of the Sisters' Islands, and they waste no time exploring, climbing lush trees and diving into shimmering lagoons. When they spot a strange boat circling the off-limits Little Sister's Island, where a hatchery for rare turtle eggs is housed, they smell a mystery they just cannot resist. Joined by a new friend, the Sengkang Snoopers brave raging rivers and winds to thwart the plot. But can they save the turtles before danger finds them?