Tormented by her high school classmates and with nowhere to turn for help, Moon Dong-eun sinks into despair before deciding on a new mission in life.

Already on edge over the past resurfacing, Yeon-jin grows more anxious when she learns about her daughter's new homeroom teacher — and of a sudden death.

While Ha Do-yeong comes across an intriguing game opponent, Yeon-jin realizes her deepest secrets are at stake when she tries to intimidate Dong-eun.

Son Myeong-o's sudden absence causes tension in the friend group. Dong-eun finds her trust in Kang Hyeon-nam tested.

Questions arise over Myeong-o, Dong-eun gives Yeon-jin a chance to come clean about her past, and the circumstances of Yoon So-hee's death are revealed.

Hye-jeong finds an incriminating recording on Myeong-o's tablet, and Hyeon-nam receives an unwelcome visitor as she prepares to send her daughter abroad.

Dong-eun's end game comes into focus as she sends Jae-jun a troubling package and orchestrates a plan to take down Yeon-jin and Lee Sa-ra.

As Sa-ra and Yeon-jin deal with the aftermath of their crumbling reputations, Dong-eun learns the details behind Yeo-jeong's private struggles.

Yeon-jin and Shin Yeong-jun panic over Myeong-o. Dong-eun takes care of a lingering problem. Yeon-jin’s mother schemes to remove a threat.

Do-yeong issues an ultimatum. Dong-eun demands a piece of evidence be handed over. Yeon-jin attempts to do damage control after old videos appear online.

As the final pieces of Dong-eun's revenge plot slot into place, she considers what comes next — and what it will mean for Yeo-jeong.