Dreamwood by Heather Mackey is set roughly 100 years ago in a slightly alternate version of the Pacific Northwest. Lucy, 12, has just run away from her boarding school to join her father in his explorations. He is a scientist specializing in clearing ghosts – however while ghosts are acknowledged by most people as real, they have begun to be dispersed by the use of electricity, and his profession is not exactly admirable anymore.
When Lucy arrives in the town of Saarthe, she discovers her father has disappeared into the wild forest of a place called the Devil’s Thumb. Helped along by a mysterious little man in a cottage, and accompanied by a boy named Pete, Lucy sets off in search of her father, as well as a cure for the disease that has been destroying the trees and everyone’s livelihoods.
With the help of a native girl, Lucy and Pete make it to the forest and begin searching for the miraculous dreamwood, a type of tree they believe will cure the rot, and hopefully lead them to her father as well, since he was also searching for it. But the forest is extremely dangerous, and they have to abide by strict rules. A sort of intermediary adversary emerges when Lucy is betrayed by someone she thought was a friend, who even has minions, but he manages to destroy himself without her help, and the real adversary is the last dreamwood tree itself, which has poisoned the forests in vengeance for the settlers’ logging activities.
Lucy ends up having to face the tree alone (although, being a tree, this final confrontation with the adversary is wordless), which has been feeding off her father in order to make its own magic. She makes a painful offering, and in turn manages to save her father and the forest.