Plot
When fourteen-year-old Jo Tiegan is shopping with her father in 1995, she notices an antique shop which she feels a compulsion to go to. There she sees a beautiful oval mirror, which she is given as a gift by the elderly owner of the shop, who comments that the mirror is meant for her. Jo is delighted, and the mirror is placed in her bedroom. That night, Jo is stunned to see the image of another girl in the mirror, instead of her own reflection, and it is obvious that the other girl, Louisa Iredale (also fourteen years old), can see her just as clearly. Louisa is able to 'introduce' herself to Jo by writing her name on a book for Jo to read. However, when Jo tries to write her name on the mirror to introduce herself to Louisa, she is startled when the pen begins to disappear into the mirror. After Louisa is called away to dinner, Jo investigates the mystery and is accidentally pulled through the mirror into Louisa's bedroom in 1919. This leads to the discovery, by Jo and Louisa, that they can visit each other's times, through the mirror, any time they want to do so – provided that the mirror is situated in exactly the same place and that the mirror's alignment and orientation are identical within the mirror's frame, at corresponding moments in 1919 and 1995.
In 1919, Louisa's father is a senior official in the New Zealand Government's Health Department, and their family house is a mansion with servants. Jo, who is the daughter of the Australian school principal at a New Zealand college, lives in a school residential building which happens to be the same house as Louisa's family home, and the girls even have the same bedroom.
When Jo and Louisa meet, there is instant rapport between the two girls and they become firm friends, and life changes for them both as they become caught up in a web of intrigue. Following Jo's unexpected journey through the mirror, a hazardous situation occurs during an archaeological dig in a well at Jo's school, when a container they discover in the well is damaged and two of the students working nearby are accidentally sprayed with toxic waste. The affected students become extremely ill, and, when it is discovered that the container has the date 1919 on it, Jo is worried that her friends' sickness is her fault because of going through the mirror to 1919.
Back in 1919, Jo asks Louisa to help her find the container so that they can move it, to prevent the later disastrous events happening in 1995. The well is located in the yard of a neighbouring house which is rented by a British visitor to the area, Sir Ivor Creevey-Thorne. Jo and Louisa enter the yard and look down the well, but are disturbed in their actions by Sir Ivor Creevey-Thorne. Their activities are watched by a teenage boy, Nicholas, whom Sir Ivor had brought from Russia to New Zealand, under the guise of caring for the boy until the dangerous situation in Russia abated. Although Nicholas is grateful to Sir Ivor for his help, he is extremely worried about his family, whom he has not heard about for a long time, and is worried about the lack of information he receives whenever he asks Sir Ivor about them. Nicholas is also upset that Sir Ivor refuses to allow him to leave the house, or to have any friends of his own age.
When Nicholas manages to escape from the house, he goes to Louisa's home, where he finds Jo's encyclopedia (which Jo had brought through the mirror to show to Louisa and her brother Titus when they have to write an essay about the Roman Empire). Intrigued by colour photographs, Nicholas checks for information about the Russian Royal Family. To his horror, he reads that Nicholas II, the Tsar of Russia, and his family, had been executed. When Jo and Louisa come into the room, Nicholas asks Jo where she got the book and demands that she tell him if the information is correct. Jo says that the book was given to her by her Dad and that the information is correct. Nicholas reveals to Jo and Louisa that he is Alexei Nikolaevich, the son of the Tsar, and that it is his family who had been executed. Sir Ivor's treachery is finally revealed. Instead of caring for Nicholas, Sir Ivor had actually brought Nicholas to New Zealand so that he could 'sell' Nicholas to the highest bidder – Russian Bolsheviks, who want to take Nicholas back to Russia with them so that Nicholas, the last surviving member of the Russian Royal Family, can be publicly executed.
Jo asks her school friend, Tama, a science student, to assist her and Louisa and Nicholas. When Louisa and Tama meet for the first time, they instantly fall for each other – with the romantic bond between them deepening as time passes. There is also a romantic bond between Jo and Nicholas. Sir Ivor, who had earlier taken Nicholas' family signet ring (saying it was for the ring's 'safekeeping'), calls for Nicholas to be brought to him and then takes the ring from a desk drawer. Sir Ivor drops the ring into a container of toxic waste – in front of the horrified Nicholas – and warns Nicholas not to attempt to retrieve his ring from the container.
Later, Nicholas, who requires his family signet ring as proof of his identity, tells Jo that the container of toxic waste is safe, as he has hidden it in the well. Jo is horrified at this and now considers Nicholas to be the person responsible for the harm which had befallen her friends at the school. Nicholas promises her that everything would be okay. With the help of Tama, and the technology of 1995, a neutralising agent for the toxic waste is discovered, and a sufficient quantity is manufactured to render the waste in the container safe.
Sir Ivor holds a ball, to which members of the New Zealand's high society has been invited (including Louisa's parents). While waiting at the fence for a chance for Nicholas to go to the yard to pour the neutralising agent in the container, music can be heard from Sir Ivor's ballroom and Nicholas teaches Jo to dance the old way. During the dance, Nicholas and Jo kiss each other, and Louisa and Tama shyly hold hands.
Back in 1995, Jo's parents are very worried that Jo is back in 1919, and they decide to confront the elderly owner of the antique shop over the matter. They are surprised when the old man welcomes them and comments that they are expected. The elderly man tells them everything, and his true identity is revealed. He upsets Jo's parents when he states that he and Jo would marry (in 1919) and that Jo would not be returning to 1995. Meanwhile, back in 1919, Nicholas pours the neutralising agent into the container. Although he is successful in neutralising the toxic waste, it will still remain harmful for many years after 1919. However, it will be safe in 1995. Nicholas is able to travel through the mirror to 1995 and retrieve his ring. However, when he attempts to return to 1919 through the mirror with the ring, he discovers that he is unable to do so because the ring already exists in 1919. Nicholas is given two choices – he can return to 1919 without the ring (and, therefore, without him being able to prove his identity), or he can stay in 1995 with Jo. After he makes his choice the mirror begins to ripple and everyone must get to the time period they wish to remain in before the mirror vanishes from both periods.
