The first week of filming The Gyeongseong Alchemist became a testament to the lightning Yoo-jin had captured in a bottle. With the initial tension broken, Kwon Ji-hyuk's confidence grew daily, his raw, untrained talent being expertly shaped by Director Oh's masterful hand. The chemistry between him and Yoon Chae-won was a thing of rare, captivating beauty—a magnetic push and pull that promised to be the fiery heart of the series. The production was running smoothly, even ahead of schedule. A dangerous sense of optimism began to permeate the set.
Disaster, when it struck, did not come with a dramatic explosion. It came as a quiet, insidious corruption, a ghost in the machine.
The scene took place in the main editing suite, a dark, cool room on the studio lot where Director Oh and Yoo-jin were gathered for their first review of the week's dailies. The mood was light, almost celebratory. They were about to witness the first fruits of their labor. The editor cued up the first scene—the one that had given them so much trouble on day one.
The visuals that filled the large, high-definition monitor were stunning. The cinematography was rich and textured, the lighting was exquisite, and the performances were every bit as powerful as they had remembered. A slow smile of satisfaction spread across Director Oh's face.
But then, the sound came through the studio-grade speakers. And it was a mess.
The dialogue, which had been so crisp and clear on set, was muddy, indistinct. It was plagued by a strange, low-frequency hum that seemed to pulse just beneath the actors' words, and it was peppered with inexplicable bursts of digital static, like a bad radio signal.
"What is this?" Director Oh demanded, her smile vanishing. "Sung-min, what is wrong with the audio?"
The on-set sound mixer, a respected veteran named Choi Sung-min with a stellar reputation, looked baffled and horrified. "I… I don't understand, Director," he stammered, his face paling. "My equipment checks out perfectly on set. The levels were clean. I monitor every take through my headphones. It sounded pristine."
They played the next scene. It was the same. The visuals were perfect, but the audio was corrupted, almost unusable. Scene after scene, take after take, it was the same story. A full week of their actors' brilliant, raw, on-set performances was potentially lost, drowned in a sea of inexplicable noise.
The production ground to a halt the next day. The entire sound department was in a state of controlled panic, running diagnostics on every microphone, every cable, every recording device. They couldn't find a single fault. They tried swapping out the memory cards, suspecting a bad batch. The problem persisted. They were losing precious time and an astronomical amount of money with every passing hour the cameras weren't rolling. Panic began to set in, and the finger of blame was starting to point toward the beleaguered sound mixer, whose flawless career was now on the verge of imploding.
Yoo-jin, however, felt a cold knot of suspicion tightening in his gut. This didn't feel like a technical glitch. It was too consistent, too specific. It felt deliberate. It felt like an attack. He quietly pulled Min-ji aside. "I want you to do a deep dive," he said in a low voice. "The entire sound department. The mixer, his boom operator, the assistants. I want to know everything. Financials, family, recent contacts. Look for any vulnerability, any point of leverage."
While Min-ji began her digital excavation, Yoo-jin took a different approach. He got a copy of the raw, corrupted audio files from the editing suite and took them back to Aura headquarters, to the one place he knew he could find a different kind of truth. He went to Kang Ji-won's studio.
"I need your ears," Yoo-jin said, handing him the drive. "And your machines."
Ji-won, intrigued, loaded the files into his state-of-the-art audio workstation. The muddy, static-filled dialogue of the actors filled his perfectly tuned studio.
"It sounds like a grounding issue," Ji-won diagnosed initially. "Or a faulty preamp. Standard technical problems."
"I don't think it's standard," Yoo-jin said. He closed his eyes, activating his Producer's Eye, and focused its perception not on a person or a piece of music, but on the corrupted sound waves themselves, visualized as a chaotic, jagged line on Ji-won's monitor. He treated the noise itself as a signal.
[Analyzing Corrupted Audio File: Scene 12, Take 3]
[Signal Integrity: 45%]
[Dominant Interference: Low-Frequency Hum (60Hz cycle), Intermittent High-Frequency Static.]
This was what any audio engineer could detect. But Yoo-jin pushed his ability deeper, searching for patterns within the chaos.
[SYSTEM ALERT: Hidden Anomaly Detected.]
[Analysis: A patterned, ultra-low-frequency (sub-20Hz) signal is embedded beneath the audible noise floor. The signal is not random. It is a repeating digital sequence. This is not corruption. This is a deliberately embedded signal designed to interfere with and degrade the primary audio recording.]
Yoo-jin's eyes snapped open. "It's sabotage," he said, his voice hard. "There's a signal buried in the noise. It's not random. It's an engineered pattern."
Kang Ji-won, the master of sound, leaned forward, his expression shifting from curiosity to intense focus. A deliberate, engineered signal was a challenge. This was no longer a technical problem; it was a puzzle. Using his sophisticated audio software, he began to isolate the almost imperceptible, sub-bass frequency that Yoo-jin's ability had detected. He ran it through a series of complex filters, carefully peeling it away from the rest of the audio.
Then, he pitched the isolated signal up by several octaves, shifting it into the range of human hearing.
What came out of the studio speakers was a strange, high-frequency, digital "chirp." It sounded like a dial-up modem, a quick, repeating burst of coded information. It was the undeniable sound of a deliberate, malicious device.
At that exact moment, Yoo-jin's phone vibrated. It was a text from Min-ji.
"Found it. The second assistant sound engineer. Lee Jin-woo. The one who handles the data backups at the end of each day. He has a younger sister with a rare, incredibly expensive autoimmune disease. Her hospital bills for the last six months, totaling over 100 million won, were paid in full by an anonymous donation from a registered shell corporation. A shell corporation owned and operated by Quantum Music Holdings."
The final piece clicked into place. They had found their saboteur. Quantum, unable to control the cast, had pivoted their attack. They were trying to cripple the production by making the sound unusable, forcing costly and time-consuming reshoots, bleeding them dry until the production collapsed under its own weight. It was a subtle, brilliant, and devastatingly effective attack.
Yoo-jin looked at the looping, chirping signal on Ji-won's screen. He now had the saboteur. But firing him would be a mistake. It would cause more delays, and it would alert Quantum that he was on to them, likely provoking an even more aggressive form of attack. No. He had to solve the problem of the corrupted audio without Quantum ever knowing their weapon had been neutralized.