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With the possibility of magic being destroyed and the fate of Storybrooke hanging in the balance, it's a race for Emma and Regina to track down Henry before Gold finds him first.

While Regina is still in shock over the death of Robin Hood, the heroes discover Gold has stolen Hades' Olympian Crystal and tethered all of Storybrooke's magic to it. Henry is tired of all the pain magic has caused his family, so he goes rogue, with Violet in tow, to destroy magic once and for all.

Despite their return to Storybrooke, danger looms for the heroes as Hades grows increasingly powerful.

Hades turns to the heroes to ask for help with getting Zelena back from Rumplestiltskin and Peter Pan. In return, he offers to take all their names off their tombstones. However, when Hook is still unable to leave, he and Emma must journey into the depths of the Underworld. Meanwhile, Cruella De Vil is determined to keep the heroes trapped in the Underworld.

Now that Hades and Zelena are reunited, Hades tells Zelena that he wants a future with her outside of the Underworld. All she needs to do is heal his heart with True Love's Kiss so they can leave the Underworld and trap the heroes there for eternity. When Regina overhears of this plan, she enlists Cora's help to find a way to separate Zelena from Hades.

Flashbacks include Ruby and Mulan end up in Oz, where they run into Dorothy. Following Zelena's return to Oz, the three ladies seek out a way to be rid of her once and for all. However, Dorothy mysteriously turns up missing, and Ruby's quest to find her new friend puts her in the Underworld. Meeting up with the heros, Ruby joins Emma, Regina and Snow in an effort to find Dorothy.

Belle turns to Rumplestiltskin with hope of finding a way to protect their child from Hades. However, they disagree over whether to use dark magic, as Belle forbids Rumplestiltskin from using his powers for evil.

Emma, Snow, David, Regina, Robin, Henry and Hook continue to look for a way to release everybody from the Underworld. At the mercy of Hades, Gold makes a portal to Storybrooke, which transports Belle, Zelena and Baby Hood to the Underworld.

Finally reunited, Hook and Emma are desperate to find a way to defeat Hades so that they can return to Storybrooke with the group. A surprise visit from Hook's departed brother Liam could be the lead they are looking for. Tired of watching from the sidelines, Henry secretly takes matters into his own hands.

Hook's captivity takes a dark turn when Hades threatens to condemn him to the River of Lost Souls after Hook's refusal to choose which three of his friends will have to remain in the Underworld. Meanwhile, Gold is suddenly eager to help the group find Hook so he can return home to Belle.

In the Underworld, an escapee from Hades' prison informs the heroes that Hook is being held captive. But before the heroes can rescue Hook, they must face a terrifying beast that guards the prison.

Emma, Regina, Mary Margaret, David, Robin, Henry and Gold arrive in the Underworld, on a mission to rescue Hook, only to discover that their search will be more difficult than they had anticipated.

The dark ones plot to destroy light magic.

Hook's transformation into a Dark One in a Camelot flashback.

Zelena and Arthur search for an enchanted relic.

Merlin gives Emma an ultimatum.

More adventures in Camelot with Merlin, Arthur and the others. Also, a flashback to a time before King Arthur tells about when Merlin fell in love with a refugee named Nimue.

Merida encounters a dangerous journey with Belle. When Emma orders Merida to kill Belle, Gold must be brave to defend her. In Storybrooke, Regina, Mary Margaret and David find a spell to communicate with Merlin but Arthur isn't successful with it.

Emma and Regina come up with a way to free Merlin, but don't have a crucial ingredient. Also, Mary Margaret and David search for a valuable dagger; Henry asks Violet on a date; and Merida tries to embark on a secret mission at Emma's request.

Lancelot warns Mary Margaret of King Arthur's plans. Also, Emma gains hope in fighting darkness because of Hook's love for her. In a Camelot flashback: Guinevere heads out on a quest when she thinks Arthur might be losing his way.

In Camelot: the heroes work hard to set Merlin free while Mary Margaret finds out what happened to Lancelot. In Storybrooke: Arthur wants David to help him capture a thief and Emma helps Hook while trying to figure out how to gain the Excalibur.

Camelot hosts a royal ball and grim events force David and Robin into action. Regina's strength is tried when she attempts to protect Emma.

In the fifth season premiere, Emma seeks help from Merling of Camelot after beginning the transformation into the Dark One. Princess Merida, King Arthur and his Knights of the Round Table assist her along the way.

Bonus "Birth" episode with special audio commentary from Cast Member Colin O'Donohue, Executive Producer/Writer David H. Goodman and Producer/Writer Jerome Schwartz.