It tells the story of urban planner Lin Mo who accidentally discovered an old drawer in his study that had never been opened a year after his father Lin Jianming passed away. The yellowed letters, incomplete engineering drawings and a rusty copper key in the drawer not only revealed the secret hidden by his father during his lifetime - a past event related to the renovation of the old city in the 1990s, but also implicated an accident that had been covered up many years ago. As Lin Mo pursues clues, she gradually realizes that her father's "accidental" death may not be an accident, and every item in the drawer is an "echo" left by her father, guiding her to piece together the truth buried by time. In the process of pursuit, Lin Mo not only re-recognized his father, but also faced his own inner confusion about family ties and career ideals. Finally, under the guidance of "Echo", he completed his confession to his father and his own redemption.
