The Pendleton family is a prominent noble clan that appears glamorous but hides numerous secrets. Sister Isabella, due to an accident, enters the Pendleton Manor as a governess to teach the family’s young son. She initially only wants to complete her work peacefully, but accidentally witnesses the "gray transactions" of the family heir Sebastian, and also discovers doubts about the death of the previous heir in the manor. Sebastian initially sees Isabella as an irrelevant "outsider," but is drawn to her purity and wisdom during their interactions; Isabella, in the process of uncovering the truth, gradually learns about the struggles beneath Sebastian’s cold exterior. Caught between family conspiracies, moral boundaries, and growing feelings, the two must eventually choose between exposing the secret and protecting each other.