Catherine Bennett donated bone marrow to save her boyfriend Mike, who had leukemia. After the surgery, however, immune complications forced her onto long-term hormone therapy, and her weight soared to 100 kg. After Mike recovered, he cheated on her and humiliated her, so Catherine resolutely threw him out of the house. On a blizzard night, she found a dragon cub named Milo on her porch, called the police, and took him in—but Milo recognized her as his mother. Milo’s father, Kaelan Voss, Chief of the North American Dragon Council, hired Catherine at a high salary as Milo’s tutor. After Catherine entered the dragon estate, she healed Milo, who had become withdrawn after losing his mother, while also getting entangled in a dragon power struggle: the maid Vera poisoned him, Kaelan’s uncle Desmond plotted assassination and kidnapping, and the noblewoman Isabella colluded with Desmond in an attempt to destroy their marriage. She and Kaelan went from suspicion to trust, from allies to lovers. She successfully regulated her body, lost weight, and made a comeback, and she refused her ex-boyfriend Mike when he demanded another bone marrow donation. In the end, Desmond and Isabella were brought to justice. Kaelan proposed, and the two held a wedding. After marriage, Catherine became pregnant and gave birth to a daughter, and the family of four lived happily ever after.