Bai 찬미 was once the most terrifying agent of the National Security Planning Department (NIS), code-named "Black Shadow".She is calm and courageous, never ruthless in performing tasks, and has completed impossible tasks on the tip of the knife many times.However, a mistaken action in her judgment caused her subordinates to sacrifice and her goal slipped away from her fingertips.That failure was like an inhealing scar, engraved in her career and heart. For this reason, she was demoted and now stayed silently in the NIS cybersecurity team, processing data and code day after day, as if the sharpness of the past has been smoothed out by time. But fate never really let her go. When a leak of a leak involving core intellectual property broke out in South Korea's largest company, senior officials were furious, and the case involved multiple forces, which was as complex as a maze.Just as the investigation was deadlocked, a name surfaced again - Bai찬미.She was chosen to go deep into the tiger's den and sneak into this war of invisible smoke with a brand new identity. This time, she not only needs to find her former self, but also face the irreversible past.