After death, a soul weighs 21 grams. Seven days later, it vanishes, and no one knows where it goes. But some souls must not remain. Someone tried to use those 21 grams in an experiment. The experiment failed. They opened a door that should never have been opened, and it could never be shut again. Ever since, souls with deep enough obsessions no longer disappear. Xie Wei guards the Seventh Site, making a living by dealing with these things. The same power is hidden within him, too. He is waiting for an answer.
