Actors Ginnifer Goodwin And Josh Dallas, Right, From The TV series 'Once Upon A Time.'
Actors Ginnifer Goodwin and Josh Dallas (R) from the TV series "Once Upon A Time&" arrive at the 15th Annual Costume Designers Guild Awards in Beverly Hills February 19, 2013. Reuters

"Once Upon A Time" Season 4, Episode 5, titled "Breaking Glass," airs Sunday, Oct. 26, on ABC. Emma Swan (Jennifer Morrison), Regina Mills (Lana Parrilla), and Queen Elsa (Georgina Haig) team up against the evil Snow Queen, aka Sarah Fisher (Elizabeth Mitchell).

Spoiler alert: This update contains Once Upon A Time Season 4 spoilers. Read at your own risk if you have not watched the previous episodes or promo videos.

In its Oct. 19 episode, Once Upon A Time Season 4 reveals a few important things: One, Captain Hook, aka Killian Jones (Colin O'Donoghue) could have his hand back, but the power it holds is "allowing" the pirate to cause harm - to others and himself. It is not cursed, but Killian is better off without it.

Two, Mr Gold, aka The Crocodile (Robert Carlyle), will not allow Captain Hook to blackmail him again. Three, the Dark One cannot ever hurt Elsa or Anna (Elizabeth Lail). Four, the Knave of Hearts (Michael Socha) is on a mission of his own in Storybrooke.

In earlier OUAT 4 episodes, viewers saw the snow queen may want to inflict harm on Emma Swan. The complete history, however, has yet to unfold. That Queen Elsa is not safe around her, however, is already clear. In the OUAT 4x5 promo clip, the snow queen unleashes more of her wrath.

With these revelations and other notable developments, Once Upon A Time Season 4, Episode 4 ("The Apprentice") lays the groundwork for the peak of the first half of the season. Henry becomes his grandpa's apprentice, which brings to mind The Seer's vision: Henry will be the Dark One's "undoing."

In Once Upon A Time Season 4, Episode 5 promo video, the evil snow queen says she will "build a snowman," taking all childhood innocence out of the context.

The plot thickens in OUAT Season 4. From the promo clip, it seems Regina Mills is getting more screentime in this week's new episode. She yells, "You ruined my life." Does she say it to Emma Swan, the snow queen, or the author of the fairy tale book?

Josh Dallas and Ginnifer Goodwin, who play Prince Charming and Snow White, respectively, have been mostly in supporting roles, as the "Frozen" arc peaks toward a mid-season conclusion.

WATCH: Once Upon A Time Season 4, Episode 5 Promo Video | ABC on YouTube ('Breaking Glass')

Once Upon A Time Season 4 airs Sundays on ABC. The next episode is (aptly) called, "Family Business."