When a revolution happened to overthrow Miranda's Imperial parents, Kim and a bodyguard took the innocent two-month-old Miranda and escaped through time. They lived on 20th century Earth, raising her as their child.
Some of the revolutionaries, led by Zevron and Sallak, hunted her down to prevent a rebirth of the oppressive Empire. The bodyguard was killed, but Kim was able to get Miranda to the Eighth Doctor. She was killed shortly thereafter. (PROSE: Father Time)