On the latest episode of "Once Upon a Time," familial love broke a curse and Glinda offered some help.

In "A Curious Thing," Regina (Lana Parrilla) says she's confused as to why Zelena (Rebecca Mader) would have given up to cast the curse. She also discovers that Henry needs to regain some of his memory if they want to defeat the Wicked Witch.

The heroes go in search of Henry's storybook to help him bring back his memories. They look in Gold's (Robert Carlyle) shop, but it's nowhere to be found. Then Snow (Ginnifer Goodwin) checks the closet, and it magically materializes.

Meanwhile, Hook (Colin O'Donoghue) is in the trunk of a car at the hands of Zelena, who is angry that he hasn't cursed Emma with his kiss. After getting out, he convinces Henry that he can help him escape to New York, but Zelena sends in her flying monkeys to prevent that from happening.

Just in time, the rest of the gang comes to Hook's aid. After rescuing them, Emma (Jennifer Morrison) tells Henry that she's done lying to him, so she hands him his book, and all of his memories come flooding back.

Zelena then drops in and steals Henry. She starts strangling him, but Emma is able to use her new magic powers to free him from Zelena's death grip.

Regina, who is not doing well, wakes up to see Henry standing over her. She gives him a kiss, and it breaks the curse, meaning everyone's memories come back.

Later, when everyone is visiting Neal's grave, Snow starts going into labor.

Meanwhile, in the Fairytale Land flashback, Aurora and Philip admit to telling Zelena about Snow's baby to save their own. Zelena then turns them both into flying monkeys, and freezes the heroes. She feels Snow's baby bump, deciding she wants to take her child.

The Charmings then go and visit Glinda, and she tells them they need some magic to defeat Zelena.

David (Josh Dallas) offers up his heart to enact the curse, which will reunite them with Emma, who has magical powers. Snow reluctantly agrees, but when she crushes his heart, Zelena shows up and puts a forgetfulness curse on them.

Nevertheless, Snow is convinced that half her heart will be enough to revive David, and it works.

Zelena then drinks a potion to retain her memories. Rumple is also about to drink it, but then Neal emerges from within him and sends the potion to Hook.

On the next episode, "Kansas," Snow/Mary Margaret will go into labor, and a young girl from Kansas will make an appearance.

The episode's synopsis reads: "With Mary Margaret in labor and due to give birth at any moment, the residents of Storybrooke go on high alert in an attempt to ensure that Zelena doesn't try to steal her newborn baby for use in her ultimate game plan to turn back time and change her destiny -- while obliterating Regina's existence. Meanwhile, in the land of Oz of the past, Glinda tries to convince Zelena to fight her evil tendencies and join her and her sister witches as a protector of Oz. But the appearance of a young girl from Kansas could turn out to be her undoing."

Watch the promo below for "Kansas," which airs Sunday, May 4 at 8 p.m. on ABC.