An anonymous tip leads the police to a hotel pool party. Do Jeong-u cracks the code to learn the location of the fourth murder.
Former FBI profiler Jamie Leighton joins the task force. Lee Ji-uk secretly tails a victim to capture footage and nail an exclusive.
When Son Min-ho is named as the next target, the team is briefed on the White Night Village tragedy. Min-ho suspects a survivor as the culprit.
After Jeong-u reveals he's from White Night Village, Jamie opens up about her dark childhood. The task force keeps a close eye on Min-ho's home.
Jeong-u is put in charge of Min-ho's protection. A news segment about the police officer's heroic rescue helps Jamie piece together key clues.
Gong Hye-won catches the criminal red-handed at the scene, but is perplexed when prosecution takes over the case. Jamie seeks answers about her surgery.
Jeong-u uses Hye-won to escape from the hospital and enter the police department. USB drives sent to Ji-uk contain footage that raise further questions.
Jamie coerces a confession out of Min-ho, while Ji-uk shows Hye-won the new videos. Jeong-u tries to find out a way to reach the foundation's boss.
At Gong Il-do's office, Jeong-u looks through files and demands answers. A photo of her father with Min-ho prompts Hye-won to revisit old evidence.
A familiar face at the crime site helps Jamie identify the third survivor. Hye-won trails Il-do as Jeong-u follows a van from the welfare center.
Jeong-u's investigation into Baek Hyeon-su's death turns up a link to Oh Jeong-hwan. Hye-won confronts Il-do about his past and current experiments.
Hye-won gains access to Jeong-u's secret archives. The truth behind the night of the tragedy is revealed inside White Night Village.
Having regained her memory, Jamie reconnects with her long-lost twin brother. Jeong-u proposes swapping Oh Kyeong-min for the secret lab's whereabouts.
Jeong-hwan expresses concern about his rapid aging. Jang Yong-sik tips someone off about Moon Jae-ung's identity and his upcoming meeting with Min-ho.
Jeong-hwan orders Min-ho to supply more test subjects for the experiment. With Jeong-u's glasses in his possession, Il-do completes the formula.
Fixated on completing her experiment, Cho Hyeon-hui uses Jamie to get Jeong-u's blood. All but two people escape the lab before the explosion.