When Zelena is enticed by a offer of a proposal from Hades', Regina has to turn to Cora in order to convince Zelena not to give in to Hades' scheme. Meanwhile, James, upset over his jealously of being favoured by his twin brother in their past, decides to finish David and get rid of Emma and Robin with Cruella's help, and Gold finds a loophole in his attempt to save Belle. In the Enchanted Forest, Cora has to bring Zelena back from Oz after Regina causes a mishap using a wand, only to have Cora end this reunion when they discover that they're related.
An Underworld windmill is placed in the red tinted forest.
In The Character's Past
In the Enchanted Forest, a young Regina wishes that her mother Cora had more time to play. Without her mother watching her, Regina finds a magic wand and attempts to transform her doll into a real sister with whom to play, only to have the spell backfire, knocking her unconscious. Cora and Prince Henry realizes that the only way to save her is by bringing a magical family member to wake her up. So Cora visits Oz ("Many Years Ago") to bring back Zelena, who just used her magic to restock the logs she dropped, despite objections from her abusive adoptive father, who doesn’t want Zelena to perform “wicked” magic. Cora immediately freezes the woodcutter as he was about to hit her (her adoptive mother wasn't around to protect Zelena this time), then gives Zelena the opportunity to prove that magic can be used for good, and she accepts. As Zelena is able to wake Regina, the two are unaware of each other being sisters at first, but over time become close and quickly realize that they’re related, leading to Cora admitting that Regina and Zelena are sisters. Despite Regina's pleas to have Zelena in her life, Cora, believing that Zelena’s presence will interfere with Regina’s future of becoming the queen, wipes both of their memories and sends Zelena back to Oz.
In the Underworld
As they look at the burning night sky over the Underworld Storybrooke, Hades and Zelena are on a date, as he explained why he created the world for her, then tells Zelena that he wants to follow her back to the real Storybrooke, if he is able to restore his heart and become human again. However, he also tells Zelena that in order to do that he wants to leave the outsiders in the Underworld forever, then he asks her to be his partner in chaos (a modified version of a wedding proposal), leaving Zelena feeling awkward. Unfortunately, Regina is seeing this through a mirror and then confronts Zelena afterwards, as the latter thinks that Hades, like Robin Hood, might not be a villain forever. Regina explain this to the rest of the outsiders, saying the only way to solve this problem is to go to Cora, who works below the Underworld Mill, and supervised by a guard and the woodcutter (Zelena's adoptive father). She finds a hook hidden under the grains, cuts the black handcuff, and escapes. Hook then finds Cora and brings her to Regina.
When she discovers the truth about Zelena's feelings for Hades' from Regina, Cora suspects that her daughter is being played for a fool by him, so she makes a potion that should make Zelena to forget about Hades. When Cora finally meets Zelena for the first time ever, this mother-daughter reunion doesn't go smoothly as planned, and even Zelena is on to what they did with the water from the River Lethe they put the spell on, as she turns down her mother’s false apology. This leads to a fight between Regina and Zelena but before this accelerates Cora restores their childhood memories of each other and she regretted the way she raises them, and apologizes to her daughters. Now that the sisters have made peace, Cora decides that it's time for her to move on from her unfinished business. As they see their mother walk toward the bridge, the flames open up but it dies down and the gate opens, allowing Cora to move on to Mount Olympus to join her husband, Prince Henry Mills. Later on, Regina gives Zelena her blessing to be with Hades, who is waiting for her at the Underworld Diner for their second date, which Zelena sees as a opportunity to reform him.
In another situation involving sibling rivalries, David is confronted by James, who he blames for being taken away from their mother and having a better life than he did with King George. After James knocks David out by using his stun gun, he tricks his niece Emma and Robin Hood to lead him to Zelena's baby. James revealed himself when they reach the rendezvous point, and is joined by Cruella, who is still looking for a way to escape the Underworld by stealing Zelena's baby for leverage with Hades. When Cruella and James enter the harbor as part of their plan to send Emma and Robin to their deaths, David and Hook arrived to rescue Emma and Robin before it's too late. David attempts to help James to move on, who believes that killing David is his "unfinished business" that kept him in the Underworld. After David's plea to help James falls on deaf ears, the twins are forced to fight each other on the edge of the dock, and David twists James off into the River of Lost Souls, condemning him forever. Emma tells her father that there was nothing he could do to save James, despite his best efforts.
In between the events, Gold is looking over Belle’s sleeping body, and despite his promise to her that he would use light magic to save her and their child, Gold decided that he's going to have to do things "his" way, through dark magic. Moments later, Gold surprises Zelena while she was en route to meet Hades. Since she was responsible for giving Belle the spindle that placed her under, Gold bought Peter Pan along as "a loophole". As he introduces Zelena to his father, Pan places a bag over her.
- James hatred of David is due to a lifelong envy of his brother getting to live with a loving family instead of the cold King George.
- The title should have been called "siblings" to be more accurate.
- Ginnifer Goodwin as Mary Margaret Blanchard/Snow White (absent)
- Jennifer Morrison as Emma Swan
- Lana Parrilla as The Evil Queen/Regina Mills
- Josh Dallas as David Nolan
- Emilie de Ravin as Belle French
- Colin O'Donoghue as Hook
- Jared S. Gilmore as Henry Mills
- Rebecca Mader as Zelena
- Sean Maguire as Robin Hood
- Robert Carlyle as Mr. Gold
- Barbara Hershey as Cora
- Robbie Kay as Peter Pan
- Victoria Smurfit as Cruella De Vil
- Tony Perez as Valet
- Adrian Hough as Woodcutter
- Ava Acres as Young Regina
- Isabella Blake-Thomas as Young Zelena
- Romuald Hivert as Guard
- Greg Germann as Hades