It's the 1970's and Emerald is 13 and living on a beach in far North Queensland called Quarantine Bay. She lives there with her father and her two younger brothers. Their mother has died, thanks to cancer and several months ago, their father who had lost custody, due to a breakdown, took off with the kids and they have been secretly traveling around Australia and have now reached here.
In better days Emerald was conceived in this forest. Their father is a solitary man still dealing with the death of his wife and his time fighting in the Vietnam war. He often leaves the children to explore and entertain themselves and in doing so his three kids have discovered something incredible.
Sandcastles are washing up on the beach. Where are they from? Who's making them? Apart from them, the beach is deserted. They come to the belief that other children on another beach are making them, and the ocean is transporting the castles here. So they start making castles for the ocean to take to these other children. But then they receive the news that the small beach is to be destroyed to make way for a port and a road to service a new mine. And before they know it their father is arrested. Emerald's younger brother Hook is taken into care. So, with her other brother Leaf, Emerald sets out to save the beach. But how? They have nothing. Not even shoes. Or do they? The town wants this mine, they want the jobs, a future. Huge bulldozers move onto the beach ready to destroy the rainforest. They remain on the sand waiting for these two kids to be found. But as Leaf observes Emerald is changing, she starts communicating with the forest, with the trees and feral pigs and even the butterflies. It will seem natural to her, but astonishing to others. But will it be enough in the face of man's greed? Despite all her courage Emerald will have to face the fact that just as she couldn't save her mother from cancer, she can't save the beach from progress. But then, the bulldozers move in and an accident occurs involving her younger brother Hook who has somehow escaped his care. The people come together to help. But together they are not enough. The bulldozer cannot be moved. But then Emerald calls on the forest for help, and the forest answers. Butterflies, millions of them leave the forest and cover the bulldozer, and with all the people helping, the bulldozer is lifted, and her brother is saved. And so is the beach. The town is reluctant to talk for fear of sounding crazy. But regardless Quarantine Bay was seen as a special beach and was left alone.