Long ago, Killian and Liam’s father left them as children. He traded them into service in exchange for a rowboat to get away from the law.
Years later in the Enchanted Forest, the Evil Queen hires Hook to kill her mother. In the process, Killian runs into his father once again. His father was caught not long after abandoning his boys and fell under a sleeping curse. It was broken by his nurse and true love’s kiss. They fell in love and she changed him into a better man. He’s so sorry for what he’s done. Regina wants Hook to kill his father to prove he’s strong enough to kill her mother. Instead Killian offers to sneak him away, then he finds out that his father has another son. Hearing his father make the same promises to his new son, Hook is enraged and kills him.
In present day Storybrooke, everyone searches for Hook in the hopes of stopping him and the Dark Ones. The Dark Ones mark them all. They plan to switch places with living souls and the ferry from the underworld will take them all to the underworld.
Emma isn’t marked and plans to fight but Rumplestiltskin tells her to use what time is left wisely and say goodbye to her loved ones.
Zelena tells Regina and Robin that she plans to raise her daughter by herself and teach her to be wicked. Regina sends her back to Oz.
Rumplestiltskin gives Belle the power to leave Storybrooke and see the world. He wants her to live out her dream and looks on sadly as she leaves.
Snow, David, and Henry decide they want to spend their last remaining moments with family and head to Granny’s to share dinner. Meanwhile, Emma comes up with a plan to sacrifice herself to save them all but she’ll need Regina’s help to do it. Emma plans to bring all of the darkness to her and destroy herself to save everyone but Hook steals Excalibur from her, derailing her plan.
As the hour nears, the Dark Ones summon everyone to the ferry. Regina reminds Hook of what he did to his father and asks him what kind of man does he want to be. When Emma tries to stop her family from being taken to the Underworld, Nimue stops her. Watching Emma in such pain, Killian tells Nimue to stop. He’s chosen the man he wants to be and pulls all of the darkness from all of the Dark Ones into Excalibur. Then he begs Emma to use the sword to destroy him and all the Dark Ones. He wants to die a hero. With no other choice, Emma does just that.
Everyone is transported to the moment where Emma saved Killian by turning him into a Dark One. He dies in her arm. She is no longer a Dark One and everyone returns to Storybrooke.
Belle returns to Storybrooke after hearing about what occurred. She reconciles with Rumplestiltskin because he was so selfless in sending her away.
Emma is awoken by whispers that lead her to Mr. Gold’s shop. It’s the dagger. When he shows it to her it has Rumplestiltskin’s name on it. It turns out he tricked Hook and used magic to pull all of the power of the Dark Ones into the dagger and turning himself back into a Dark One once again.
In return for not telling Belle, Emma makes a deal. She wants Rumplestiltskin to allow her access to the Underworld so she can save Killian. She plans to share one heart with him the same way David and Mary Margaret do and Emma and her family board the ferry to the Underworld.