Hook is overtaken by the darkness and remembers his hatred of Rumplestiltskin as he becomes the Dark One. Now he wants his revenge against the Crocodile.
Lancelot tries to get to the Lady of the Lake, his mother, hoping she will help them.
Emma finds Hook and tells him she’s no longer afraid of their future but they have to fight the darkness together. They need the help of those they love. But the darkness manipulates Hook and turns him against Emma. She has Excalibur but hid it from him. He reminds her that he’s always trusted her but she obviously doesn’t trust him.
Emma uses Excalibur to summon Hook. He’s furious that he doesn’t have any control. She gives him Excalibur saying that she does trust him and she wants them to get the darkness out of the both of them by doing it together. She tells him she loves him. Hook is shocked. He’s used to having to say it first. Then he says he loves her too.
Hook tricks Emma and takes Merlin’s heart. Hook wants to get back to Storybrooke but to do so he needs to crush the heart of the thing he loves the most. Instead of crushing Emma’s, he plans to crush Merlin’s and as all Dark Ones live in him, Nimue is also crushing his heart allowing him to enact the curse.
Emma tries to stop him. She tells him that his revenge is not his happy ending. She is. If he destroys this heart, he’ll destroy his happy ending with her. Hook says that happy ending died the moment she turned him into a Dark One and he crushes the heart.
Emma can’t reverse his curse but she can make him forget what he’s done and that he’s the Dark One. She erases everyone else’s memories as well. She’s determined to fix it all herself as she adds a memory wipe to Hook’s curse.
Zelena restrains Emma with the anti-magic cuff while the new Dark Hook takes her memories.
When Emma wakes up she tells Regina, Snow, and Charming that she turned Hook into the Dark One. She admits that she was going to destroy Zelena. Snow points out that there had to be another way. That would be premeditated murder. They try to retrieve their memories but all of the dreamcatchers are gone.
Hook finds Belle and Rumplestiltskin at their shop. He wants to duel with Rumplestiltskin on his ship. He even taunts Rumplestiltskin with Excalibur which is the only weapon that can kill Hook. Emma offers to protect Rumplestiltskin if they take off the anti-magic cuff. Not even Henry will trust her since she lied to them all about her plan.
Rumplestiltskin tells Belle he won’t run. He wants to fight with honor and he does manage to fight off Hook.
Zelena comes to the hospital to take the baby but she’s gone. Regina takes her to the baby. Robin says that Zelena is the baby’s mother and she can see her as long as Robin or Regina are present.
Regina has Merida guard Emma when Hook arrives and knocks her out. He calls Emma an anchor who was nothing more than a pretty, blonde, distraction. He wants to hurt her like she hurt him.
Emma finds Henry and asks for help. No one was ever better at figuring out how to break a spell than Henry. They decide this is Operation Cobra Part Two. Henry uses a locator spell to find the dreamcatchers but Hook has them protected. Henry takes off Emma’s cuff to allow her to use magic to get to them.
Belle meets Rumplestiltskin at the well but tells him that he’s broken her heart too many times for her to take him back. She doesn’t know if she wants to make it work and she has to figure things out on her own and protect her own heart.
Emma gives everyone back their memories. Emma now knows what Hook is doing. He really wanted Rumplestilskin’s blood because he’s died and come back. They’re at the portal to the underworld which they can now open. A ship from hell appears and Nimue steps off, in the flesh. All of the Dark Ones are now in Storybrooke.