Mary Lennox is introduced in colonial India. A cholera epidemic kills everyone around her, including her parents. She is found hiding behind her dead ayah and is to be sent to England.

Mary arrives at Misselthwaite Manor. She meets the gruff housekeeper Mrs. Medlock, travels across the Yorkshire moors, and receives her first impressions of the estate's gloomy grandeur.

Mary wakes to the moors under a grey sky. Martha, a cheerful Yorkshire housemaid, talks to her frankly and mentions the locked walled garden. Mary's curiosity is sparked for the first time.

Mary learns about Dickon, Martha's brother, who can charm wild animals. She skips rope for the first time and asks more questions about the walled garden.

The robin leads Mary to a buried key. She finds the keyhole in the ivy-covered wall and enters the secret garden for the first time.

Mary works in the garden each day and meets Dickon at last. He arrives carrying animals, brings her seeds and tools, and they begin the garden together. That night, she hears crying in the corridor.

Mary follows the crying and discovers Colin Craven — her cousin, who has been hidden in a locked room. They talk through the night. Colin reveals he believes he will die and grow a hump like his father.

Colin and Mary continue meeting. Colin has a tantrum when a servant fears he will get a hump; Mary confronts him angrily and tells him he brings his illness on himself. He is shaken.

Mary and Colin share stories. She tells him about Dickon and the garden, carefully not revealing its location. Colin demands to be taken there. Spring begins to arrive on the moors.

Colin asks to meet Dickon. His animal companions are introduced to Colin, who is dazzled. The plan takes shape: Colin will be wheeled to the garden when it is ready.

Colin is wheeled into the secret garden for the first time. He is overwhelmed by the beauty. He meets Ben Weatherstaff over the garden wall. The three children begin working together.

Colin discovers he can walk. He practices in secret with Mary and Dickon. He becomes obsessed with the idea of 'Magic' — the life force he feels in the garden — and leads the children in a kind of ritual.

Summer ripens. The garden reaches its full bloom. Mary, Colin, and Dickon work every day. Colin grows stronger and more confident. He decides he wants to surprise his father by being healthy when he returns.

Colin begins asserting authority in the garden with increasing confidence. He wrestles with Mary, tests his physical capabilities, and confronts a tantrum with self-awareness for the first time.

Susan Sowerby, Dickon and Martha's mother, visits the garden and sees the children. She sends a warm message to Archibald Craven urging him to come home. The children continue their summer work.

Archibald Craven, wandering in Austria, feels a shift. He dreams of his dead wife. He receives Susan Sowerby's letter. He turns and comes home.

Archibald returns to Misselthwaite. He walks to the locked garden. The door bursts open and Colin — running, upright, glowing with health — crashes into his arms. Father and son meet each other, truly, for the first time.