After receiving a call from Hong Hee-joo's kidnapper, Paik Sa-eon attempts to learn more about him — only to find it's hard to escape his surveillance.

Sa-eon works quickly to track down the caller, forcing Hee-joo to stay hypervigilant. Despite her fears, she continues to play along with the ruse.

After Sa-eon experiences an attack, he grows wary of Hee-joo's relationship with her friend. Meanwhile, an ominous figure makes his presence known.

After receiving the ominous call, Hee-joo abandons her clandestine plan. She then undergoes a tough interview with Sa-eon — sharing an intimate moment.

Sa-eon grapples with feelings of betrayal after learning the truth about Hee-joo. However, when she receives good news, they begin to grow fonder.

Sa-eon and Hee-joo's relationship shifts after her harrowing rescue. Determined to catch the kidnapper, Sa-eon goes full force — with the help of 406.