This article is about the episode. For the character, see Nimue (character).
Middlemist flowers are scattered in the forest.
In the Characters' Past
1,000 years earlier before "the age of Arthur" (1,500 years before the Present Day), Merlin and a friend were trekking through the desert desperate for water. Merlin continued to see a light and ran after it, revealed to be the Holy Grail. When his friend grabbed it, he turned to ashes. Merlin then grabbed the grail after praying to God, and was able to drink from it. When he put his hand down, he realized he had magic. The desert was no more — only lush greenery and forests. 500 years later, Merlin is at a village where his apprentice informs him of a woman who escaped a burning village. Merlin encounters the person, and introduced herself as Nimue. She wants revenge on Vortigan, the masked man responsible. She also had Middlemist flowers to offer, but Merlin agrees to help her and places the seeds in a planter and heads to the village.
As they reach the now damaged location, Merlin suspects that Vortigan is after the Holy Grail, but Nimue thinks that Merlin should kill him, wishing that she had the magic to destroy him. Merlin on the other hand, wants that he would give up his magic and immortality to be with her. When they reach Prometheus, Merlin uses part of the flame forging the sword that would become Excalibur, only to be joined by Vortigan, who then took the sword but as Nimue tried to fight him she was killed. Just as Merlin was going to challenge Vortigan, Nimue pulled out the Dark One's heart, revealing that she had already drank from the Holy Grail and had only faked her death. Even as Merlin pleaded with her not to crush Vortigan's heart, Nimue crushes it, becoming the Dark One. and then severed the sword in half so no one else would have the power.
In the current universe, Hook was upset with Merlin, thinking he was not helping Emma at all as Hook sees her making Dreamcatchers. But Merlin tells Hook that he is going to help her as he knows what it means to lose a loved one. Merlin tells the residents they need to bring Excalibur from Arthur while he takes Emma with him to Prometheus to acquire the spark needed to reunite Excalibur with the dagger. Before they go on their mission, Hook gives Emma a necklace with a ring as reminder of their love. As Emma embark on this quest, Merlin told her that the quest could force her to choose between light and darkness that could have dire consequences for the twosome. As they reached the location, Merlin had brought the dagger with him and showed it to Emma in order to use the power. As Emma looked into the dagger it rolled back the names of previous Dark Ones, until they saw Nimue, who appeared to them, as she was the original Dark One. When she tried to attack Merlin, Emma protected him. Nimue stressed that Emma had to protect herself, then forces Emma's hand to choke Merlin's throat, with Nimue telling her to finish him off. However, Emma fights it off by telling Nimue "I'm not nothing. I've never been nothing. The power you have I don't need!" and pulled out Nimue's spark, which was the key ingredient needed, but didn't crush it as Nimue warned her it wasn't over yet.
Meanwhile, the residents were coming up with plans to get back into the castle, but Zelena already knew a way in having studied the place, on the condition that her powers were restored. As Regina, Hook, David, and Robin sneak their way into the castle, Regina asked Mary Margaret to watch Zelena. Unfortunately at the same time Arthur had other plans for the residents as he showed Guinevere a potion that melts anything if it touched them. It also turns out that Zelena had double crossed her fellow Storybrookers by tricking Mary Margaret with contractions, then knocked her out and tied her up. When they reached the Round Table, they were ready to take the sword from Arthur, only to discover that Zelena was working with Arthur and tethered the sword to read Merlin's inscription and Arthur summoned him. As Merlin and Emma returned to Camelot, Emma discovers Merlin missing, as he has appeared in front of Arthur and informs him Emma had passed the test, and he had what he needed to unite Excalibur. Arthur refused to give Merlin the sword in hopes of achieving more glory, then order Merlin to render them powerless and with the exception of Zelena made them disappear.
In the basement, Emma had both the dagger and the sword, as the manifestations of both Rumplestiltskin, Nimue, & previous Dark Ones appeared. She then uses the spark she took from Nimue and forged the dagger and Excalibur together, making it whole again. Despite the warnings of Merlin never to touch Excalibur, Emma ignores the message and takes control of the sword, making her the most powerful Dark One ever.
- The word Nimue is a Celtic word that translates to The Lady of the Lake.