In the Great Sheng Dynasty, humans and demons coexist. Sang Ning, a half-demon, has lived on Demon Mountain since childhood. Later, she is brought into the prince's residence to marry in place of the frail Prince Regent, Bo Wang. Possessing the extraordinary ability to dispel evil energy, she unexpectedly cures Bo Wang's long-standing illness. Together, they investigate sealed cases from the past, gradually falling in love along the way. Hand in hand, they unravel the mysteries and eliminate the hidden threat disturbing the peace between the two races, ultimately finding happiness and tranquility through their mutual support.