Backing Camelot, Emma comes back with the spark of Prometheus and tries to get Henry out of Granny’s when Merlin shows up and freezes everything. Arthur wants Merlin to kill Emma’s family if she won’t return the spark to him. 

Henry shows her Operation Light Swan. He and Hook were looking for a home. Emma says she needs to use the darkness one last time. 

Emma battles Zelena and Arthur and manages to get Merlin to fight Arthur’s hold over him but Merlin ends up catatonic but she saves her family. Later, Emma still can’t light the spark. Regina tries to use the dagger to get Emma to admit what’s holding her back but Hook and Snow stop her. 

Emma tells Hook she’s scared because she wants a future with him. When they kiss, the spark ignites. 

In Storybrooke, David confronts Arthur who runs and when Hook catches up, Arthur tries to kill him. Emma shows up with Excalibur and saves him. Hook wants to know why she needs the sword. She says she’s doing all of this for him and then disappears. 

Hook is determined to find out what happened to Emma in Camelot. He goes to Rumplestiltskin. He tells Hook that he needs to give Emma a reason to find him. 

Emma uses dark magic to fast forward Zelena’s pregnancy. She goes from two months to nine months pregnant in moments. Apparently she needs the cries of a newborn to help wipe out light magic. Zelena has a baby girl but Emma grabs Zelena instead of the baby. 

Turns out that Emma’s house in Storybrooke was the one that Hook chose for them. She shows it to Hook, tells him she has a plan and the next thing he knows he wakes up chained in the basement next to Zelena. 

Emma admits that she’s trying to destroy the dark magic inside of her. The darkness needs to be contained in a vessel and she plans to put it in Zelena and then kill her with Excalibur. Hook uses his enchanted hook to take off the band preventing Zelena from using her magic. Zelena runs off while Hook stays to try and reach Emma. 

Hook finds squid ink hidden in the house and uses it to detain Emma and get answers but Zelena returns. She wants the Dark One to pay so she stabs Hook in the chest but he doesn’t die. Zelena shows him his memories through a dreamcatcher where she’s about to reforge Excalibur but Hook almost dies because Arthur had cut him with it in the woods. A wound from Excalibur is fatal. 

Emma used Excalibur to tether Hook to it and save his life, knowing that it will only increase her darkness and tether itself to him. Hook becomes the new Dark One. 

Excalibur now has both Emma’s and Killian’s names on it. Killing Zelena would have destroyed the darkness in them both.