Charmaine house sits for her Great Uncle's magical house, discovers a plot to overthrow the kingdom and finds the royal Elf gift that has been lost for many generations. Charmaine Baker is a young girl who loves to read so much she often doesn't do anything else. Her parents think it might be time to stop spoiling her and force her to do some practical work for once. She is asked to house sit for her great Uncle William, a wizard who will be traveling to the land of the elves in order to get treatment for a debilitating sickness. Though the whole affair seems tedious, Charmaine is excited that she will be nearer to the Royal Libraries as she has always wanted to do some good work with books. When she arrives at Great Uncle William's house, she is given many tasks most of which require magic which Charmaine has no experience with. Before she can explain herself, her Great Uncle is taken away by the elves. The wizard does, however, leave behind his bedraggled dog, Waif, to keep her company.
Simple chores like doing laundry, cooking and navigating her way from room to room prove very difficult to do without magic. Charmaine finds her Great Uncle's library and reads about how to do some simple spells as well as more fun spells – like flying. One day while she is practicing flying she encounters an insect-like creature called a Lubbock. Charmaine escapes the buzzing Lubbock only to run into a little blue man who is a Kobold that calls himself Rollo. Apparently, Rollo takes care of the garden and after unsuccessfully trying to swindle Charmaine, he disappears. Later that night, as Charmaine is trying to settle in, she receives another visitor – a young man named Peter who claims to be her Great Uncle's new apprentice.
Charmaine is visited by a troupe of Kobold who are all angry at her because she won't take their advice in terms of how to manage the house. In the end, all the Kobold decide to go on strike – refusing to do any cooking or gardening or cleaning for Charmaine. Peter teaches Charmaine how to do basic housework without any magic and Charmaine gets grumpier and grumpier as Peter's spells always seem to go slightly wrong and cause more trouble than they're worth.
The next day, Charmaine visits the King and Queen, who have agreed to let her help the Princess sort out the books in the Royal Library. While Charmaine is there, the Princess receives visitors. She introduces Charmaine to a witch called Sophie Pendragon who has also brought her son, a little toddler named Morgan and a fire spirit called Calcifer. Later on, they are joined by another little boy named Twinkle who turns out to be Howl Pendragon, Sophie's wizard husband, in disguise.
When Charmaine returns to her Great Uncle's home, she is disgusted at the mess Peter has made. Peter tries to use some magical spells he learned to clean up the mess but he causes more problems so Charmaine has to “cancel” all his spells. Later on, the two discover a suitcase containing a key to the house as well as a complicating map of the house. Apparently there are unexplored "paths" in the house that the wizard himself doesn't know about. Charmaine discovers a passage that leads to the Royal Library which she can use to go to work. Peter discovers a passage that leads back in time, where he startles a past Great Uncle William. Peter tells Charmaine that he had an extensive conversation with the past Great Uncle William and learned that when the old wizard bought his house, he was hoping that one of the passages might lead to the King's lost treasury.
As Charmaine is going to work one day, she rescues Twinkle, who has gotten caught up on the golden roof of the royal mansion. Twinkle tells her that he and Sophie have been hired by the Royals to search for the lost Elf gift, something the elves gave the Royals centuries ago that is supposed to guard them. Twinkle asks Charmaine to help him discover more information by searching through the books in the Royal Library. One day, Charmaine almost gets run over by the reckless Crown Prince Ludovic and is warned by a villager not to say anything untoward about the Crown Prince because apparently he has Lubbocks working for him. Later on, an elf visits Charmaine to give her three Lubbock eggs that were removed from her Great Uncle and tell her that her Great Uncle is recovering very well. It tells Charmaine that only the fire spirit Calcifer can destroy the eggs.
At work in the Royal Library, Charmaine is officially introduced to Ludovic and she notices that his eyes are purple indicating that he has Lobbockin blood. Charmaine borrows Calcifer from the Royal Library and brings him back to the Great Uncle's House. On the way back, they see Rollo accepting a pot of gold from a Lubbock then the Lubbock laying eggs in Rollo without the Kobold noticing. Calcifer destroys the Lubbock and also the Lubbock eggs but it takes a lot of magic and Charmaine and Peter worry that the fire spirit is gone.
The next day, Charmaine captures Rollo in a magical bag and bring him to the other Kobolds. Charmaine tells them that Rollo was being paid by the Lubbocks to cause trouble between the Kobolds and her Great Uncle. After apologizing for their bad behavior, the Kobolds lead Sophie to Prince Ludovic's castle where Sophie witnesses the Prince using Kobold servants to discover the lost treasury and siphon away the money to his own hideout.
Charmaine hurries to find Sophie to tell her what she has discovered about Prince Ludovic and also inform her that Calcifer's been missing for a few days, now. On the way there, she is joined by Calcifer who tells her that he knocked himself out from the magic but he's fine. Charmaine arrives at the Royal Mansion just in time to see Sophie and the King have an argument while Prince Ludovic watches. Suddenly, a nursemaid and a lady transform into Lubbocks and snatch up Twinkle to threaten Sophie to leave. Twinkle eludes the Lubbocks and shows Charmaine and Sophie where Prince Ludovic has hidden the King's treasure – under the Royal Mansion's golden roof.
The King and Queen find out Prince Ludovic is a Lubbock and they tell him that he can no longer be the next ruler because of his tainted blood. Twinkle transforms back in the wizard Howl. With the help of Calcifer, Howl transforms Prince Ludovic into a rabbit and then Waif pounces on him. Howl then tells the King that the Elf gift is none other than Waif, the dog.
The story ends with everyone saying goodbye to Sophie, Howl, Morgan and Calcifer.
Best part of story, including ending:
I thought the Great Uncle William's house was very interesting because I haven't ever read a house that is as confusing and as full of personality as the one Diana Wynne Jones describes in this book. The house sounds like a fun house to live in and exploring its various wings and passageways would probably be endlessly entertaining.
Best scene in story:
My favorite scene was when Peter finds the passageway that takes him back in time to have an absurd conversation with a young but unruffled Great Uncle William. It was funny how the Great Uncle was so un-surprised that Peter is from the future because he got lost while living in his house.
Opinion about the main character:
I like that Charmaine changes from a slightly spoilt and self-absorbed young girl to a more mature and capable young woman. I like that Charmaine is clever and observant and doesn't let the Kobolds and Lubbocks bully or frighten her.