The Secret Island

Siblings Peggy, Mike, and Nora endure abuse from Aunt Harriet and Uncle Henry after their parents vanish on a flight to Australia.

They join friend Jack, an orphan, to flee to a hidden island where they build a willow-tree house, grow food, care for animals, and hide from searchers.

Strange events reveal a kind monk protecting an owl sanctuary, leading to twists including the parents' rescue and the guardians' arrest.