In Episode 5 of the fifth season of "Once Upon A Time," David and Mary Margaret attempt to retrieve the dagger of the Dark One. Emma used a dreamcatcher to look into the past and know how Merlin was turned into a tree and then she and Regina get to know the important ingredient they needed to free Merlin.
Using the dreamcatcher, Emma saw that Merlin was turned into a tree by a Dark One who wore a gold mask. It started with Merlin telling the Dark One that he destroyed the only woman he loved. When he was about to stub the Dark One, he hesitated and dropped the knife. The Dark One then cast a spell and Merlin became a tree.
In Camelot Mary Margaret and David told Regina that it would be better to give the dagger to Arthur for Emma's sake. Regina brought them to where she hid the dagger. Emma appeared and froze her parents, telling Regina that they were under Arthur's spell and he wanted to reunite the dagger with the Excalibur. Emma further told Regina that they needed to free Merlin using the dark magic and she's willing to take the risk. A tear of lost love turned him into a tree, so another tear could free him. But when they used Emma's tear, it didn't work.
Henry invited Violet for a dance and he received some tips from Hook. Regina was stunned and threatened Hook. However, the date didn't work out well and that brought Henry to tears. Regina wiped them and told Henry he can be a hero in their world. Emma then performed the spell and Merlin was freed.
Meanwhile, Belle came in saying Rumple was missing. Emma holds Gold as a prisoner because she needs him to obtain the Excalibur. Gold asked her why she's doing it but Emma refused to reveal her plans. Rumple told her she might push her loved ones away because of what she's doing.
