Mary spends all of the next day in the garden and vows to see Colin the next day. However, she wakes in the middle of the night to a terrifying sound. She hears people walking around and knows that this must be Colin throwing a tantrum. Mary covers her ears, but it does little to block out Colin's screams. The screams start to make her angry and soon, she feels as upset as she thinks he sounds. Suddenly, the nurse bursts in, pale and scared-looking, and begs Mary to come and try to calm him down. The nurse is thrilled to see that Mary isn't afraid and encourages her to scold Colin.
It's both humorous and telling that the nurse believes that the only way to calm Colin down is by asking a child to do it: this suggests that Colin is beyond the reach of rational adult authority figures, while also suggesting that someone like Mary, who can act like a mirror for his bad behavior, will be far more effective in making him see how ridiculous he's being.
Mary feels angrier and angrier the closer she gets to Colin's room. She burst in and shouts that everyone hates him and will let him scream himself to death. Nobody has ever said this to Colin and it surprises him. Mary threatens to scream if he screams. Through his sobs, Colin says he can't stop screaming, to which Mary replies that this is all just hysterics. Colin insists he can feel the lump and he'll die, but Mary insists that this isn't true and asks for the nurse to come and show her Colin's back. Colin wants Mary to look so that she'll sympathize with him.
Colin's response to Mary's shouts reinforces that because Mary is spoiled and wants her way, just like Colin, she can make him see how silly his tantrum is for a boy his age. However, it's important that Colin believes he can feel the lump starting, as it suggests that his negative and fearful thoughts are powerful enough to create phantom sensations that to him, are very real. Modern readers will know that such deep-rooted anxiety can, in fact, manifest itself in physical symptoms, so it’s possible that Colin truly believes he can feel the lump forming.
The nurse pulls up Colin's shirt to expose his thin back. She tries not to laugh at the sour and serious look on Mary's face as Mary carefully inspects Colin's back. After a minute, Mary exclaims that there are no errant lumps and threatens to laugh at him if he says he has lumps again. The narrator notes that if Colin had ever thought to ask questions, or had ever lived somewhere where people weren't afraid of him, he'd know that all his maladies were the work of his scared mind. He begins to wonder if Mary is right.
When the narrator offers their assessment of Colin's situation, it's made very clear that the fear and secrecy surrounding his condition—whatever he thought it actually was—is what made it into something meaningful. Mary's ability to tell him without fail that there's no lump gives him something to cling to, which helps him feel better and in control.
The nurse says that she had no idea that Colin thought he had a lump on his back, and says that his back is just weak because he refuses to sit up. This shocks Colin, and he cries in secret relief for a minute. Then, he asks the nurse if he could live. The nurse, remembering the London doctor's words, says that if Colin goes outside and doesn't act so horrible, he might. Colin reaches out a hand towards Mary and she takes it. He says he'd like to go outside and meet Dickon and his creatures. The nurse makes Colin's bed, gives the children tea, and then tells Mary to go to sleep. Mary offers to sing Colin her Ayah's song and sends the nurse to bed.
The nurse's ability to reinforce Mary's diagnosis shows that once the veil of secrecy is lifted, many more people can become reliable figures in Colin's life. By bringing up the London doctor's diagnosis, the novel suggests that that doctor was correct, but that Colin just didn't want to hear it at the time when he saw that doctor. This indicates that Colin needed to be ready to heal; it wasn't something that another person could make him do.
Once they're alone, Colin asks if Mary found the garden. Mary says that she has, but she'll tell him everything tomorrow. Colin says that if he can get into the secret garden, he's sure he'll grow up. He asks her to softly tell him what the garden might look like to help him fall asleep and Mary complies. She talks about roses, the spring, and crocuses.
Colin's assertion that he'll live if he can get into the secret garden again reinforces the power of secrets among children, as this secret allows him to transfer his attention onto something just as powerful: friendship and nature.