February 5, 2012. A little girl named Seowon is reported missing from a playground. Police launch an investigation and question witnesses and suspects, but Seowon's case is never solved. Twelve years after Senior Inspector Jeon Gyeong's retirement, she is visited by a young police officer: a woman who pleads with her to reexamine Seowon's case. But with each uncovered memory, only one thing becomes clear: everyone in Seowon's vicinity was lying.