Childhood in this novel is presented as something that is truly magical and wonderful, but ultimately, something that is evanescent, ephemeral and fading. This is the overwhelming message of the novel as Tom slowly begins to work out that as he goes back in time he is seeing the inevitable passing of time occur. This is reflected starkly in the comparison between the massive garden behind the house that is the site of so many adventures for Hatty and Tom and the miserable back yard that the garden has become in the present. In the conversation that Tom has with Mrs. Bartholemew, Tom is forced to confront the fact that childhood is a stage that inevitably passes. Note what Mrs. Bartholemew, the adult Hatty, says to Tom, about what she learned after the tall fir-tree was struck with lighning and it fell:
And then I knew, Tom, that the garden was changing all the time, because nothing stands still, except in our memory.
Childhood is therefore one of those things that inevitably passes and does not stand still. It is only resurrected through Mrs. Bartholemew's memories. Tom, at the end of the book, has learnt that childhood is something that will inevitably pass, but that the magic and wonder of it is something that can stay with him into his adult life if he chooses. This is something that is symbolised at the end of this novel when he hugs Mrs. Bartholemew as if she were a little girl.