Erin hears that Shaju's older sister has been engaged. But while eating a rice cake, Soju, Shaju's sister, suddenly falls ill. Soh-yon diagnoses Soju's illness as "Mock milkweed poisoning" a poisonous plant that was mistaken as a plant used in the cakes. Soh-yon decides to ask her clan, the Mist People, for the medicine.

Joh-on decides to have the entire family move to his summer cottage in the mountains. While cleaning his regular home, Erin finds out that Joh-on used to be a teacher. But when Erin finds Nuk and Mok sick from eating some rotten food, Joh-on comes and helps Erin read a book about poisonous plants. He decides to teach Erin, Nuk and Mok about animal breeding and plants.

Erin begins to take care of Lilan and finds out that Lilan won't eat anything, and has been eating her fur. When she hears Lilan's cries, she comes up with the idea to use her harp to try to communicate with Lilan. It didn't work, until she fell asleep and accidentally hit the harp under her blanket.

A new teacher, Kirik, comes to Kazalm Academy from the capital. The new teacher is a royal agent whose entire family was killed by Wajaku poison. While on a stroll, Erin and Lilan fall off a cliff, but are saved due to Lilan regaining her ability to fly. Kirik watches Erin flying on Lilan and is shocked that an Ohju is flying with a human on its back. While watching them in the sky, he mistakens Erin for his sister Taya.

Erin and the others take the Graduation test with all of them passing. Erin takes the top seat in the scores, meaning that Erin can stay at Kazalm as a Master. The Shin-Oh gives her blessing to Lilan's baby and provides more funds for Kazalm. Each one of them leaves Kazalm and reminisces about their memories.

Beastinarians from Lazal come, learning about Erin's ability to tame Ohju without the use of a Silent Whistle, despite the fact that she is supposed to carry one under Law. They order Erin into using the whistle on Lilan, but Erin refuses. As one of the beastinarians blows a whistle, Lilan goes into a blind rage and injures the beastinarians. This forces Erin to use the Silent Whistle on Lilan. The Whistle gives Lilan a horrifying aftershock and she bites off several of Erin's fingers. This causes Erin to understand what her mother meant by "Ohju are beasts." From there, Erin decides to go onto the path of the "Beast Healer" a beastinarian who shares the joys and pains of the Ohju and uses the Silent Whistle, just like her mother did with the Touda. Erin is ordered to go to the Royal Palace with Lilan and her family.