In the room, Geng Xiangdong seemed to have aged ten years overnight, sitting dejectedly on the edge of the bed with lifeless eyes.

Su Tang didn't speak, but gently placed the slightly yellowed black and white photo on the chipped wooden table in front of him.

Geng Xiangdong's gaze slowly shifted to the photo. When he saw the young man in the photo smiling brightly, his whole body froze. But after only a second, he turned his head away, as if to hide his guilty conscience.

Su Tang stood quietly to the side, observing Geng Xiangdong's expression.

Seeing that Geng Xiangdong reacted to the photos, her suspicions were largely confirmed.

She then handed him a cup of hot water, using this as a starting point to elicit further discussion.

"Engineer Geng, would you like to talk to me about Wang Fei? Some things weren't appropriate to delve into back then, but now is the best time. Deputy Commander Liu... is a leader who values ​​principle but also human relationships; he will give you the best and fairest explanation..."

A long silence followed.

Geng Xiangdong slowly raised his bloodshot eyes and looked at Su Tang, the young girl who had exposed his deepest wounds but was also the only one who could bring him hope. She finally revealed the secret that had been buried in his heart for six years.

“Wang Fei… he is my son. He was raised by my ex-wife and took her surname.” His voice was hoarse. “We worked in the same company, and to avoid suspicion and gossip, we… never made our relationship public.”

"Six years ago, something happened in the team. The higher-ups concluded it was an accident. But... the only survivor, He Jing, was my most outstanding student. He went mad after returning from Devil's Slope. In his madness, he grabbed my hand and kept repeating one sentence..."

Geng Xiangdong's eyes were filled with pain and regret: "He said... 'Teacher... it wasn't poison gas... it wasn't poison gas...'"

“I suspected there was more to my son’s death than met the eye, so I started investigating in secret. But just when I was about to find something, one day I found a note in my desk drawer.”

He closed his eyes, as if the words on that note were still imprinted in his mind.

The note read: 'If you want He Jing to live, shut your mouth.'

“I’m scared…” Geng Xiangdong clutched his hair in anguish. “I’m really scared! I’ve already lost a son, and I can’t let my closest student be silenced by them too! I’m even more afraid that more young people will go to that hellhole to die! That’s why… that’s why I desperately stopped you… I’m not a mole… I’m just a useless father…”

Emerging from Geng Xiangdong's room, Su Tang felt incredibly heavy-hearted. She immediately recounted her findings and deductions to Deputy Commander Liu in detail.

In the study, after listening, Deputy Commander Liu remained silent for a long time, only taking deep drags on his cigarette.

"Bastard!" He slammed his cigarette butt into the ashtray. "The real mole actually used Geng Xiangdong's weakness, threatening him with his student's life for six whole years!"

“This person is extremely well hidden, has exceptional mental fortitude, is located within the research institute, and is very senior; otherwise, he wouldn’t know about the past relationship between Engineer Geng, Wang Fei, and He Jing,” Su Tang calmly analyzed. “If we force him to confess now, he definitely won’t admit it, and we have no evidence.”

"What can we do? We can't let him continue to get away with it!"

Su Tang's expression hardened: "Deputy Commander Liu, we can't just arrest him by force; we have to make him slip up on his own."

"Tell me about it!" A glint flashed in Deputy Commander Liu's eyes.

"Use their plan against them."

The next day, a joint announcement issued by the military region and the research institute was posted in every corner of the institute.

The announcement stated:

An investigation revealed that Comrade Geng Xiangdong did bear significant responsibility for negligence, but considering that he voluntarily provided information on some of his accomplices, this was considered a meritorious service to atone for his crime.

In order to thoroughly investigate enemy special forces, the military region decided that the special service company would escort Comrade Geng Xiangdong back to Devil's Slope to re-examine the secret mine and search for important equipment lost by the enemy.

Meanwhile, the announcement revealed that, in order to honor the fallen heroes, an excavation will be conducted at the former camp of the exploration team that perished six years ago to search for and bring back the martyrs' belongings to comfort their families.