A serial murder devours a woman every fourteen days, leaving fragments of ancient poems at the scene. The sixth deceased was the informant "Sparrow" who was buried in the dark places of the city by Interpol Qin Yan. Before she was killed, she circled the seventh date on the calendar with a red pen.
Criminal psychology consultant He Ran was parachuted into the task force. He deciphered the murderer's "sacrifice map" from the sequence of strange beasts in "The Classic of Mountains and Seas" - the six dead corresponded to six pages of "remnants of paper." The murderer regarded himself as a restorer and had to "reframe" an unjust case thirty years ago through seven killings. When Qin Yan found out that he was targeted as the seventh "sacrifice", He Ran activated the reverse psychological model: he predicted every move of the murderer and set a fatal trap in the Song Dynasty rare book exhibition hall of the museum.
But at the last second when the flames ignited, the murderer's choice exceeded all predictions. He opened a line of words that his father had hidden on the title page of an ancient book thirty-four years ago, and changed the sacrifice from "completed" to "returned". In the end, there was no seventh dead person, only a restored Song Dynasty phoenix scroll and an empty display cabinet - the phoenix flew away, but the book was still there.
