Eun Ha-won is a bright, hardworking high school student who dreams of becoming a teacher but suffers from the loss of her mother and the cold treatment of her stepfamily. Her life takes a dramatic turn when she is recruited by the wealthy Chairman Kang to move into 'Sky House,' a luxurious mansion where his three estranged, rebellious grandsons reside. Her mission is to transform these spoiled heirs into a cohesive, responsible family, all while navigating the complex dynamics of their immense wealth and personal traumas. As Ha-won attempts to tame the wild Kang cousins—the lonely rebel Ji-woon, the playboy Hyun-min, and the gentle musician Seo-woo—she finds herself caught in a whirlwind of romance, jealousy, and family secrets. Along with their loyal bodyguard Lee Yoon-sung, the 'four knights' begin to soften under Ha-won's influence, leading to a journey of self-discovery and unexpected love that challenges the rigid social hierarchies of their world.