Famous celebrity, Gu Xin, unknowingly caused the death of three individuals who became wandering souls. These souls refuse to leave Gu Xin alone until she helps to reduce their "weight" by fulfilling their last wishes before they can head for reincarnation. Each soul must only weigh 21 grams before they are allowed to reincarnate and Gu Xin who is the only human who can see them becomes their last hope. Through the journey, the cold and aloof Gu Xin learns the true meaning of love and letting go.