Stepping back from the narrative, the narrator explains that people are discovering things all the time. In the last century alone, people discovered that thoughts are "as powerful as electric batteries" and that bad thoughts can be as damaging as scarlet fever. The narrator insists that while Mary was filled with bad thoughts, she was ugly and yellow. As she learned about the robin and Dickon, she got better. Colin experienced the same thing; he was never going to get well while he focused on lumps and his fears, but once he got into the garden, good thoughts took over.
By situating Colin and Mary's story in a greater narrative of the power of thought, the narrator suggests that this is the main takeaway of the novel: positive thoughts can change a person for the better, while negative thoughts can condemn someone to a life of fear and anger, like how Colin used to live before finding the garden.
The narrator says that at the same time as the secret garden is "coming alive," along with Colin and Mary, Mr. Craven is wandering around Europe as he's done for the last ten years, thinking of how heartbroken he is. During this time Mr. Craven has forgotten his home, and his thoughts poison the air. He only stays a few days in each beautiful place. However, after leaving Mary and giving her permission to grow a garden, he takes a walk in the Austrian Tyrol and sits by a stream. He gazes into the stream and notices all the growing things. After a while, he stands and says that he almost feels alive. The narrator notes that this happened at the same time that Colin entered the secret garden and declared that he was going to live forever.
Notice that the narrator suggests that Mr. Craven has forgotten his home. Especially when considered alongside the way the novel vilifies India, this suggests that one's home—and specifically, one's English home—is the only place where a person can truly grow and flourish. Traveling, on the other hand, will lead to negative thoughts and in the case of Mr. Craven, isn't an effective way to deal with his grief. The fact that Mr. Craven starts to improve when Colin enters the secret garden shows that positive thinking can affect others.
Mr. Craven sleeps better that night than he has in a long time. This brief period of calm is short-lived; he soon wanders on and returns to his dark thoughts. The good moments continue to occur, however, and he doesn't know that he's coming alive at the same time as the garden. As the summer progresses, Mr. Craven starts sleeping better. His body grows stronger and his soul feels better too. He starts to think about going home and wonders how Colin is doing.
Specifically because Mr. Craven starts to think more about Colin as he improves, the novel offers some room for someone to interpret "home" to mean a person, not just a place. Just as Ben is able to make Colin's Magic work within his own faith tradition, this allows the reader to think of home in a way that works for them.
One evening, Mr. Craven falls asleep at the edge of a beautiful lake. He dreams that Mrs. Craven is calling to him from the secret garden and wakes up to a brilliantly beautiful morning. A servant is there and offers Mr. Craven his mail. As Mr. Craven flips through it, he remembers his dream and thinks that the garden is locked and the key is buried. He has one letter from Yorkshire. It's from Mrs. Sowerby, asking him to come home.
While not exactly the work of Magic, Mrs. Sowerby's letter offers the reader another example of how to help someone else through positive thought: in this case, by doing something concrete and asking for something specific. When combined with the dream, this is shown to be one of the most effective ways to create change.
Mr. Craven arrives in Misselthwaite a few days later and realizes he's thinking often about Colin. He realizes that he didn't intend to be a bad father, but he'd never felt like one and had inadvertently neglected the boy. Mr. Craven wonders if ten years of neglect is too long to recover from. The narrator notes that this thought represents bad Magic, but Mr. Craven doesn't yet know how to properly use Magic. Mr. Craven decides to stop in and see Mrs. Sowerby on his way to Misselthwaite. He finds only eight of her children, however, as Mrs. Sowerby is helping a woman with a new baby. He gives the children money and starts off across the moor.
When the narrator picks apart Mr. Craven's thoughts and applies Colin's tenets of Magic to them, it shows that the narrator intends the reader to take what they've learned about Magic and apply it to their own lives. Further, by suggesting that Mr. Craven will go on to learn how to properly use Magic, the novel suggests that anyone can learn and harness the power of positive thinking.
On the drive across the moor, Mr. Craven thinks of how calming and beautiful the moor is and vows to find the key to the secret garden and open the door. When he arrives at Misselthwaite, the servants notice that he looks better. He summons Mrs. Medlock immediately and asks her about Colin. She explains that nobody can figure out if he's better or worse: he started eating and then stopped; he's stopped throwing tantrums and started going outside; and he spends all his time outside with Mary and Dickon. He also laughs. Mrs. Medlock says that Colin is in the garden now. This piques Mr. Craven's interest and he heads outside, walking slowly, in the direction of the secret garden.
Mr. Craven's belief that the moor is beautiful shows that though he's been an unhappy man since his wife’s death, he has the capacity within himself to find beauty in nature. This again shows the reader that this capacity exists within everyone, no matter how miserable and bogged down in negative thinking they may be. His understanding that he needs to trust the truth of his dream and head for the secret garden suggests that the dream was the work of Colin's Magic and his wife's spirit.
When Mr. Craven gets to the walk by the walls covered in ivy, he walks slowly and tries to remember where he buried the key. He hears strange sounds from within the garden that sound almost like children playing and trying to stay quiet. Finally, he hears them laughing and running and the door flies open. Colin and Mary burst out and Colin runs straight into his father's arms. Mr. Craven looks over his son and Colin introduces himself, explaining that the Magic in the garden saved him. He declares that he's going to be an athlete, and Mr. Craven joyfully sees that his son is a normal, healthy boy. Colin says that he's going to live forever.
Colin and Mary's exit from the garden mimics a birth of sorts; they leave the maternal and safe world of the garden and enter into the adult world where Colin's father lives. However, the things that Colin tells his father shows that he's ready to make this transition and inhabit the wider world. Now that he knows how to use Magic, he also knows that it's not something unique to the garden: he can make it and use it anywhere.
Mary and Colin show Mr. Craven into the garden and show him all the autumn flowers in bloom, including roses. Mr. Craven says that he thought the garden would be dead, and they all sit under a tree. Colin tells his father his story, and as the boy speaks, Mr. Craven becomes even happier. At the end, Colin says that his good health doesn't need to be a secret anymore, and he's never using the wheelchair again.
Allowing Mr. Craven into the garden allows Mr. Craven to come to terms with his wife's death and see the garden as responsible for Colin's health more than her death. By offering him the ability to reframe, the garden introduces him to the power of positive thinking.
While all this is going on in the secret garden, Ben Weatherstaff sits in the servants' hall drinking beer with Mrs. Medlock. Mrs. Medlock wants to know if Ben's seen Colin or Mr. Craven, but Ben says only that he's seen the two together. Mrs. Medlock asks how Colin looks and Ben replies that everyone is going to discover a secret. A minute later, Ben points across the lawn. Mrs. Medlock shrieks and all the servants race to the windows. They see Mr. Craven walking with Colin, laughing.
Now that Colin's secret has come to an end, everyone at Misselthwaite will be able to be happy and healthy. This reinforces that in order to be good and helpful, secrets need to have an end date—and adults shouldn't endeavor to keep secrets from or about children, as the children will inevitably find out and rise above, as Colin did.