The book is set in a castle in a country estate in the West Country. Three children, Gerald, James and Kathleen, discover this enchanted castle while exploring this during school holidays. The Lake, Woods and marble statues, with white towers and turrets in the distance, form a fairytale setting. At the center of the labyrinth in the rose garden of the castle the boys discover a fabulous Princess asleep.
The "Princess" tells them that the castle is full of magic. She shows him the treasures of the Castle, including a magic ring that she says is a ring of invisibility, but when she actually becomes invisible she panics and admits that she is the niece of the governess, Mabel and she was just acting.
The children soon discover that the ring has other magical powers. The enchanted castle was written for adults and children. It combines imaginative descriptions, children play on the sly that recalls the story of the treasure seekers, with an increasingly compelling magic.