The Stolen Lake (Wolves Chronicles #4)

Blurb

The Stolen Lake is a children's novel by Joan Aiken, first published in 1981. Taking place in an alternate history, the story follows the adventures of Dido Twite in a fictionalized version of South America.
The novel is the fourth in the Wolves Chronicles, a series of books set during the fictional 19th century reign of King James III. In this world, part of South America is occupied by Ancient British colonists following an invasion hundreds of years before.