Hawaiian siblings Pili and Ioane "E" were New York-raised in Brooklyn. An avid geocaching fan, she wins a competition that earns her free tuition to a summer camp in the Catskills. Pili can't go in the end as they temporarily relocate from New York to Oahu with their mother Leilani to help her father, Kimo as his health and financial issues are becoming serious.As Pili is so into geocaching, her malaise at being separated from her beloved New York is assuaged by secretly liberating an old diary from her grandfather's art studio, set up in an old bus. Just as she's sneaking off the bus, she meets local boy Casper who helps cover for her.That night, as Pili is trying to secretly read the diary, E catches her. He explains the term Night Watchers to her, trying to scare her, explaining they are ghosts of fallen warriors who protect the island.Meanwhile, E is distracted from his own search for better Internet signal by local girl Hana, who is Casper's friend. She, on the other hand, is not impressed by his attitude towards the younger kids.In the diary of the ship the Peruvian's quartermaster Monks, he documented Robinson and Brown's excursion on the island. The privateers had mutinied, burned their ship and taken the treasure ashore. Monks stayed to protect the treasure while his superiors died. He gave the diary to Pili's ancestors for saving his life.Kimo catches Pili with the diary. Initially angry, he ends up taking the enthusiastic girl to see some of the landmarks in it. He falls, breaking a rib. While Leilani is distracted with Kimo in the hospital, Pili and Casper sneak off to seek the lost pirate treasure. E and Hana follow close behind.They end up having to follow the instructions in the diary as all four slide inwards of a cave too far to back out. They have to crawl through a narrow tunnel, it's opening is called 'The Jaws of Death' and it is lined with stalactites. Fearing a deadly spider, E hurries frantically out of the tunnel, leaving behind the ship journal as it's inside Casper's backpack as it collapses. Finding a mini rope bridge over a lava-filled crevice, they realize it's too deteriorated to cross, but the fearless Pili and Casper inch around it on a narrow ledge. E helps Hana maneuver around it, partially by distracting her singing a favorite song.E confides in Casper that the brown violin spider bit him, leaving him with a huge blister, possibly indicating necrosis. To not alarm the others, he covers it with duct tape. Arriving to a pool, they realise the next tunnel is filled with rain water. Pili gets through it piggybacking on E.Arriving at 'ground zero', Pili and Casper go in search of the treasure while E talks with Hana. He tries to convince her to send in her application to Julliard, but she fears it might change her too much. Pili and Casper examine the complex pulley and rope system they had remembered from the journal. Realizing one of the counterweights is down, they deduce they can access the treasure room by putting all of their weight on the severed rope.Once in, they all are collecting large amounts of gold and jewels, when Hana spots a religious statuette indicating they are in a type of tomb. Realizing the treasure is an offering, she insists they can't take anything without waking the Night Watchers. When E refuses to believe it, they awaken.All four drop their treasure and head for the pools below using the banyon roots. Everyone makes it, although E has to be resuscitated. As they move away from the mountain Leilani catches up with them. The Night Watchers approach them as they seek shelter in a shed. Pili makes an offering with a few treasures she'd kept. They are bowing down, averting their eyes when their father Kua steps out. He had died 11 years ago while enlisted. Leilani, Pili and E have a brief moment before Kua and the other Night Watchers disappear into the ocean.Leilani calls a family meeting and proposes they decide as a group if they all stay in Hawaii or Brooklyn. We then see videos of the happy family staying in Hawaii and Ioane and Hana are a couple. (thanks to Wikipedia)