Princess Irene lives in a large house, ‘half castle, half farmhouse’, on the side of a mountain. She is cossetted and loved by the whole household, who look after her while her ‘king-papa’ is away travelling his kingdom. Little do they know that an army of goblins far below the ground is planning to storm the castle. To defeat them, Irene must rely for help on the miner boy, Curdie, and on her beautiful, mysterious great-great-grandmother, who secretly inhabits the castle tower.