A Tale of Time City was first published in 1987 by British author Diana Wynne Jones. It tells the story of a girl, Vivian Smith, who is kidnapped while being evacuated from London during World War II and caught up in a struggle to preserve history. In this novel, Jones explains time travel with more reference to our current understanding of science than she does in many of her other works.
This story begins as Vivian is evacuated from London to the country during World War II. She is kidnapped by two boys, Jonathan and Sam, and taken to Time City, which exists outside of 'History'.Actions in the novel take place in Time City, the purpose of which is to oversee the course of history; their Time Police attempt to stop actions that would change history from the path that the city believes is correct. Jonathan and Sam kidnapped Vivian because they believe that she is the "Time Lady," a figure of vaguely malevolent power for much of the story, and that she is causing trouble in history that could lead to the fall of Time City. Many of their beliefs are later shown to be incorrect. Though Sam and Jonathan quickly realize that they have the wrong girl, they cannot send Vivian back to her own century because it would draw the attention of the Time Police to their actions. The three are caught up in a search for four caskets, Iron, Silver, Gold, and Lead, that are integral to the existence of Time City, and, in the end, in an effort to save Time City itself from both the machinations of a family who wishes to rule Time City, and from the end of its predetermined existence. However these caskets have been scattered through time and thus created the "Unstable eras". They are also guarded by their respective guardian.