On their first day as partners, detectives Kang Do-chang and Oh Ji-hyeok pick up a series of calls with perplexing connections to a closed murder case.

Intrigued by emerging claims of Lee Dae-cheol's innocence, Jin Seo-kyeong asks Do-chang for a meeting; the police search for the missing girl.

Unable to ignore new CCTV footage of Dae-cheol, Do-chang and Ji-hyeok look for answers; Seo-kyeong receives a troubling call from Park Geon-ho.

Do-chang visits Lee Eun-hye at the hospital; when Ji-hyeok sends Seo-kyeong a photograph of a suspect, she realizes she's in immediate danger.

After discovering a connection between Oh Jong-tae and the woman murdered five years ago, the detective squad begins working on the case in secret.

To secure a retrial for Dae-cheol, Do-chang comes clean about a slip-up in the original investigation; Seo-kyeong shares her suspicions with her boss.