Explosive vapors escape from an underground storage tank. Keahi investigates, hoping to prevent further casualties, but he runs into corruption at the Hawaii Department of Water, Wind, and Sun. Meanwhile, Liko returns to Hawaii for another summer vacation. He is now a high school senior. He rekindles his crush on Toi who is passionate about scuba diving. And then Liko drops a bombshell: he wants to scuba dive the dangerous lava tubes at Shark's Cove just north of Waimea Bay.