In The Island of Adventure, the story begins with Philip, Dinah, Jack, and their younger brother, Lucy-Ann, spending their summer holidays on a remote island. They are staying at a peaceful, somewhat isolated house, but things quickly take a turn when the children discover that the island is hiding a mystery. The children, along with their pet parrot, Kiki, soon find themselves in a series of unexpected and dangerous situations.

As they explore the island, they uncover hidden caves, mysterious people, and signs of a secret plot. With their curiosity piqued, the group embarks on an adventure to unravel the island's secrets, facing obstacles and dangers at every turn. The children use their wit and courage to uncover hidden treasures, solve puzzles, and confront villains.

Throughout the book, Enid Blyton weaves together suspense, excitement, and a sense of camaraderie between the characters. The children’s bravery, quick thinking, and teamwork are crucial to solving the mystery. The Island of Adventure is a perfect blend of mystery, action, and the joy of discovery, making it a favorite among young readers.