In the 1890s, Conor and his family live on the sovereign Saltee Islands. He spends his days studying the science of flight and exploring the castle with the king's daughter. His life changes when he discovers a deadly conspiracy against the king. When Conor tries to intervene, he is branded a traitor and thrown into jail. There, he has to fight for his life, as he and the other prisoners are forced to mine for diamonds in inhumane conditions. There is only one way to escape imprisonment, and that is to fly.