When Yeong-jae gets accepted into a top medical school, his mom becomes the envy of the other mothers, who all want to know just how she managed it.

While everyone’s still reeling from the shock of what happened, a new family whose background and values seem very different moves into Sky Castle.

Han Seo-jin confronts the entrance exam coordinator. Lee Su-im joins the Sky Castle reading group, but it’s nothing like what she expected it to be.

Sky Castle is abuzz about the pending vote but Cha Min-hyeok is confident. Seo-jin will do anything for Ye-seo – and stoop as low as deemed necessary.

Seo-jin runs into Yeong-jae and tries to talk to him. Su-im ponders what to do about Ye-bin. No Seung-hye and Min-hyeok scramble to formulate a plan B.

Seung-hye challenges Min-hyeok head on. Seo-jin thinks that she’s fixed things but doesn’t count on Kang Jun-sang. Ye-bin finds an unlikely confidante.

Running mates Kim Hye-na and Hwang U-ju are the favorites in the school election, but Seo-jin colludes with Min-hyeok to ensure that their kids win.

Kang Jun-sang delights in Seo-jin’s plan to host a dinner as an occasion to gloat over the other couples, but things get heated over Su-im’s new book.

Seo-jin incenses Kim Ju-yeong with her reply, and leads the charge against Su-im, but pays a heavy price for her shortsightedness in more ways than one.

Seo-jin relents and has Hye-na move in as Ye-bin’s tutor, but makes a startling discovery. Su-im meets Yeong-jae’s father to get his side of the story.

Su-im hears a strange fact about Kim Ju-yeong. Seo-jin’s fury boils over. Min-hyeok basks in his daughter’s stories, but Seung-hye spots something odd.

Crushed by the truth about Se-ri’s life in Cambridge, Seung-hye fears the repercussions of Min-hyeok finding out. Su-im gets a request from Yeong-jae.

Seo-jin lambastes Kim Ju-yeong but realizes she’s no match for her own daughter’s insolence. Seung-hye reflects on her choices and takes a stand.

Hye-na is rushed to the hospital, but Jun-sang orders Hwang Chi-yeong to operate on another patient. Seo-jin asks Ye-seo what she did at the party.

Not caring if U-ju is sacrificed, Seo-jin begs Kim Ju-yeong to save her daughter, but Ye-seo insists he’s innocent. Su-im infers a sinister motive.

Jun-sang reproaches Seo-jin and his mother about Hye-na. Seo-jin has harsh words for Kim Ju-yeong but has only one thing on her mind: Ye-seo’s future.

Jun-sang wants to go to the police and exonerate U-ju, but Seo-jin won’t let him. Seung-hye doesn’t want to live with Min-hyeok – and the kids concur.

Su-im pleads with Seo-jin, who remains determined. Ye-bin tells her mother what she thinks of her. U-ju wants to know why he should forgive Seo-jin.

U-ju announces he’s taking a break from school. Jun-sang resigns and Seo-jin readies to leave Sky Castle. Seung-hye prevails and Su-im’s book comes out.