Nest Freemark is a fourteen-year-old girl from Hopewell, Illinois, who is gifted with magical powers bequeathed to her from her mother's lineage. She is one of a rare few in the world who can see the spiritual warfare underlying the events in the real world. Nest is enlisted to guard the nearby park and wilderness, a regional feeding ground for feeders, as many generations of Freemark women before her. She is aided in this task by a six-inch tree-like sylvan named Pick, an insightful barn owl named Daniel, and an ethereal wolfen creature named Wraith, who appears at opportune moments to protect Nest.
Nest has the ability to see things in the magical faerie world. With this ability, she is able to see her friend Pick, Wraith and the creatures simply known as feeders. Additionally she has some sort of power over the creatures known as feeders. If a feeder is to make eye contact with her, the magic flares within her and strips the feeder of its life in a single gaze, just an instant is all it takes. The feeder will collapse in a heap and be melted into the earth in a black stain.
In the first book of the Word/Void series, Running with the Demon, on July first Nest and Pick the sylvan rescue Bennett Scott from the feeders when Wraith appears to fend them off and help her escape.
The following morning, Nest meets up with her friends, including Bennett's older brother Jared, upon whom she has a crush. Nest uses magic to knock a teen bully Danny Abbot to the ground to protect her friends. Later that day, an alarmed Pick leads Nest into the park forest and shows her a great oak tree which is actually a prison for a Maentwrog - a powerful magic beast known for devouring multitudes of people. The demon has weakened the tree and the maentwrog is threatening to break free, but Nest and Pick do a patch job to strengthen the tree's integrity.
At dinner, Nest is introduced to a traveler named John Ross, who claims to have known Nest's mother, but his true purpose for being in Hopewell is to track and defeat the demon as he is a "Knight of the Word", charged with helping preserve the balance between the Word (the representation of goodness and light in the world) and the Void (the summation of evil and darkness).
That evening, Nest sneaks out after dark to meet with O'olish Amaneh, whom she ran into earlier that day. O'olish Amaneh is the last of the Sinnissippi tribe that used to live in the area, and invites her to dance with the spirits of the Sinnissippi. At midnight, he summons the spirits of his tribe and dance among them. Nest sees a vision of her grandmother as a young lady, running with feeders and interacting with the demon and Nest struggles with the meaning of her vision.
The next day, July 3, Nest and John attend church when they find the feeders crawling all over, invisible to the congregation, but Wraith appears and scares them off. The feeders have never entered the church before, and Nest realizes that the demon must be nearby. The demon confronts her in a wing of the church, threatens her, and demonstrates his power by killing a church member. That night, the demon influences Danny Abbot to tie up Nest and leave her in a cave. The demon comes to Nest and taunts her, telling her he can do anything he wants to and she is powerless. Nest is rescued by her friends and grandfather.
While everyone is otherwise engaged, the demon confronts Nest's grandmother, Evelyn Freemark, at the Frehouse and is surprised to find that she no longer has magic of her own. She assaults him with a shotgun, and he kills her. However, Nest finds a secret note telling her to trust in her magic and in Wraith.
Finally, on July 4, Pick is captured by the demon, and Nest and John confront him at the site of the maentwrog tree where it manages to release the maentwrog. John is able to defeat the maentwrog with his magic, but passes out. The demon confronts Nest and teaches her of her past. She learns that her grandmother once became friends with the demon as she thought him simply another person, not a demon. The demon tried to seduce her grandmother, but she resisted, and turned to the side of the Word. In revenge, the demon seduced her daughter, Nest's mother, and she bore him a daughter, Nest. When Nest's mother found out after Nest was born that he was a demon, she apparently lost her mind and committed suicide. Now the demon is back for Nest, and by touching her, he can convince her to join the Void. Wraith appears, but the demon reveals that Wraith is actually a gift from the demon, sent to protect Nest until he could come back and claim her. But when he is about to lay his hand on her, Wraith turns on the demon and tears him to pieces. Nest learns from Pick that even though Wraith was created by the demon, her grandmother long ago expended all of her magic to convince Wraith to defend Nest against the demon as well.
The next day, Nest and her grandfather decide to be foster family for Bennett Scott and she visits the hospital and uses her magic to bring Jared out of his coma after a beating by his abusive stepfather.