After attending a mentor's funeral, Fang returns to the police station and finds himself embroiled in two murder cases that happened 15 years apart.

As Fang's solo investigation raises more suspicion about himself, Hsu receives an unusual job offer from the Sevenleaves Foundation.

Following clues from an old photo, the police track down a man named Wu Chun-lu. Later, Fang runs into Hsu at Sevenleaves.

While Hsu starts to question Lin Ming-cheng's integrity, Fang discovers more unsettling leads that point him toward someone he admires.

The investigation reveals a link between the serial killings and a past crime. Fang disregards Hsiao-meng's efforts to help solve the case.

The search for a deserted bus brings the police one step closer to the truth. Fang and Hsu grill Ming-cheng about what happened 15 years ago.

The emergence of a new suspect dramatically redirects the investigation, forcing Fang to race against the clock to locate the serial killer.

With his life at stake, Fang needs to survive a deadly encounter. Meanwhile, Hsiao-meng and Hsu must risk everything to save their loved one.