Once Upon a Time ventures down the yellow brick road to uncover the story of the Wicked Witch on tonight’s episode, “It’s Not Easy Being Green.”

Witches, and cyclones, and emeralds, oh my! Tonight’s season 3, episode 16, “It’s Not Easy Being Green,” tips its cap to The Wizard of Oz several times as it explains the truth behind Zelena’s past and reveals her plans for the future. Check out our full recap for what lies down the yellow brick road!

Twisted Stories: One way to arrive in Oz is via cyclone. A pair of travelers on the yellow brick road stumble upon a baby in a basket tied with a green ribbon. The husband does not want to take in the baby after watching her move a tree with a wave of her hand, but his wife insists on raising her inside the city of Oz.

In Storybrooke, Neal is lain to rest in the forest. At a wake in Granny’s Diner, Hook checks in with Emma, who would rather throw darts than try to process her anger with alcohol. Although vengeance will not make her feel better, Hook proposes something that may take Henry’s mind off of the whispering crowds. Killian takes Henry out to the docks to share the stories of the boy he took on board the Jolly Roger. Their quality time may help both of them process Neal’s death.

Zelena’s foster father teaches her to always put on her best face no matter what you feel inside. Not a practitioner of his own advice, Zelena’s father openly disapproves of her magical abilities. Zelena heads to Oz to consult the man behind the curtain, the Great and Terrible Wizard of Oz. The wizard tells her about Cora’s decision to abandon her firstborn after she realized that Zelena would never be able to marry into royalty.

The wizard grants her non-copyrighted silver slippers to take her to Rumpelstiltskin, the man responsible for teaching her sister. Showing up in Regina’s room, Rumple discovers Cora’s secret first daughter and recognizes Zelena shows great promise, but her jealously stands in the way of a breakthrough.

Sister, Sister: Tinker Bell attempts to strike up some gossip at Neal’s wake when she spots Robin’s lion tattoo. Regina tries to avoid the mistakes of her past, but when Zelena arrives, she leaves Regina to find out the truth of their relationship and promises to meet her for a showdown on main street at dark.

Down in the vault, Regina finds a letter that proves she is connected to Zelena and will fight her own battle. Regina ventures to the woods, rereading the letter and searching for a haven to process her revelation. Unfortunately, an admirer interrupts her train of thought.

Robin inquires what the piece of paper she clings to reveals about her past. When the master of pickpocketing produces the slip of paper, Regina allows him to read the note, revealing that the discovery of Cora’s first born is the most powerful sorceress ever known. Regina had taken comfort in the fact that she was the subject of the letter during her years of struggle and held onto the confidence the paper gave her. Unfortunately, it was talking about someone else. If the man who taught her everything about magic understands no one can match Zelena’s power, what chance does Regina have?

Back in the Enchanted Forest, Rumpel guides Zelena through fueling her magic with anger and keeping it in check with happiness. Unfortunately, the happiest moment in Zelena’s life is when Rumple admits she is a truly gifted sorceress. Zelena begins to fall in love with the idea of acceptance, and perhaps the charm of Rumpelstiltskin, but when he suggests that he is still training Regina, the more powerful (and greener) side of Zelena shows.

Zelena approaches Regina sitting idly at her nightstand and stabs her in the neck. The vision of Regina turns into Rumpelstiltskin and he informs her that she is disqualified from his project. The curse that Rumpel prepares to cast over the Enchanted Forest may only be unleashed by one of Cora’s daughters. Vying for her chance to finally be important to another person, Zelena fails Rumpel’s test and he chooses Regina to cast his curse.

The curse must be set by someone who is willing to lose the one thing they care about the most. For Zelena, the only thing she cares about is Rumpelstiltskin. That will not do.

Heart of the Matter: In the streets, Zelena and Regina, both clad in fabulous black outfits, come face to face. However far Zelena pushes Regina, her cunning nature proves victorious when Zelena attempts to steal Regina’s heart.

Taking a stab at Zelena, Regina reminds her sister she had the privilege of learning from Cora that a good witch never brings her heart to a fight. As Zelena flies off into the night, Regina realizes that with David’s courage and the desire for Regina’s heart, Zelena is brewing a powerful curse.

In the past, Zelena takes her rage to the wizard and tears down the curtain masking the ordinary man from Kansas, and Emma’s ex-beau, Walsh. He is a collector of magical items and hoped Zelena would recover an object from Rumpel. Zelena turns him into her puppet, a flying monkey, and begins her mission to change the past and create her second chance in a world where Regina never existed.

Regina takes good care to make sure her heart is protected by someone she trusts with it. Robin asks why she chooses to have a thief look after something valuable, but Regina informs him that giving him her heart is not the same as taking it without permission.

Hook and Henry spent the night away from the commotion on the streets and instead set their eyes on the stars. Teaching Henry the art of navigation with a sexton, Hook tells Henry that he once taught his father to do the very same task after taking him on board his ship after Neal lost his father. Henry takes some comfort from the tale, but is now filled with more questions, such as how Hook manages to be the same age as his dad. Hook tells Emma that Henry deserves to know the truth.

Watch Once Upon a Time season 3, episode 17, “The Jolly Roger,” Sunday, April 13 at 8 p.m. ET.