The secret garden blooms, and soon the robin's mate lays eggs. Everyone in the garden seems to know how precious they are, though at first, the robin anxiously monitors Colin and Mary. Dickon speaks robin so he's nothing to worry about, but the robin is wary of the slow way that Colin walks—it's suspiciously catlike. The robin finally decides that Colin is safe when he remembers how, as a fledgling, his parents made him take short flights and decides that Colin is probably just learning to fly.
By offering this chapter from the robin's perspective, the novel shows through its form how Colin, Mary, and now, the reader and the robin are learning to think of others outside of themselves. When the robin decides that Colin is learning to fly, it shows that just like the children, he has to learn compassion and empathy too.
The robin watches Colin eventually start to move like Dickon and Mary, which is comforting, but all of them perform strange movements and actions every day. Because Dickon does these things too the robin concludes that they're not dangerous and settles in to keep watch over his eggs.
The strange movements presumably refer to Bob Haworth's strength training exercises, which suggests that this is one part of the Magic that isn't rooted entirely in the natural world.
When it rains, Colin has to stay inside and pretend to be ill on his sofa. One rainy morning, Colin complains that he's so full of Magic that he can't stay still, and he and Mary discuss how horrified everyone would be to see him stand. They note that they can't keep this up for too much longer and hope that Mr. Craven will come home soon. Then, Mary tells Colin about her rainy day poking around the house, where she discovered the many rooms that nobody goes into. Colin thinks that it sounds like a secret garden and suggests that they go play in the rest of the house.
Again, learning about all the secrets within the house sparks curiosity in Colin, just as the secret garden made him curious about the outdoors. This curiosity about the house, however, suggests that Colin is growing, developing, and is getting ready to break free of the garden's constraints. The house is his father's realm, and the curiosity about it indicates that he's getting ready to join Mr. Craven.
Colin rings for his nurse and tells her that he wants help getting up the stairs, but then he wants to be left alone with Mary so they can look at the house. Colin and Mary run up and down the hallways, do Bob Haworth's exercises, and look at the portraits. Colin muses that the portraits are all his family members and points out one that looks like Mary. They play with the ivory elephants and discover that the mouse family has grown up and moved out. They eat all of their lunch, which pleases the cook.
When Colin can point out portraits that look like Mary, it indicates that he too is learning to think of people other than himself and recognize things about people. This suggests that now, he's a better friend to Mary as he better understands and sees who she is.
That afternoon, Mary notices a change in Colin's room but doesn't say anything until he brings it up. He says that he's taken the curtain off of Mrs. Craven's portrait because it doesn't make him angry anymore. He explains that two nights ago, he woke up in the middle of the night and felt full of Magic, and the Magic made him pull away the curtain. Now, he likes looking at her and thinks she was a "sort of Magic person." Mary remarks that Colin looks like an incarnation of his mother, and he slowly says that if he were his mother, Mr. Craven would like him. He admits that now, he'd like to tell his father about the Magic and cheer him up.
By deciding that Mrs. Craven was full of Magic, Colin chooses to come to peace with his mother's death. When Mary sees how much Colin looks like his mother, it shows that she too is developing the ability to recognize familiar things all over. This in turn allows her to connect with Colin, as evidenced by the fact that he chooses to share this very personal shift in his thinking with her in the first place.