Later that night, David had been summoned to meet King Arthur at the round table. He entered the room, and seeing the king at the table, David approached him. "You wanted to see me?" he asked.

King Arthur turned his head when he heard David. He nodded. "Yes. Yes, we have something serious to discuss. Please, join me. Now that you're a member of the Round Table, it's time to share Camelot's greatest secret." King Arthur took Excalibur out of its holster and showed it to David. At how the sword was missing the end. "The sword that made me king is broken. For years, I've hunted its missing piece. A piece that is known as the dagger of the Dark One."

David took a look at the sword and then back at King Arthur. So he wanted the dagger, too? And now it was his daughter's dagger. "I've heard tales about it."

"Well, I think you're the man to help me find it. After all, you're the only one who needs it as bad as I do. You're desperate to destroy the power of the Dark One."

"Only Merlin can do that," David stated.

"Perhaps. Perhaps not," King Arthur shrugged. "No one knows what Merlin wants, but with that dagger, we wouldn't need Merlin. I could reforge Excalibur into the sword it was with the power to destroy the Darkness once and for all. Can you help me in this quest?"

Meanwhile, Emma was in her chambers at Camelot, widdling away at a firm stick. She had been trying to sleep, but she couldn't. This was the only way to pass the time. Making dreamcatchers. But there were too many voices that she could hear. Voices whispering that were distracting her from her work. Always distracting her. They wouldn't leave her alone.

"Do you hear it?" came Rumplestiltskin's voice as he peered down at her. "A sweet sound, don't you think? But, also, a strange sound. Let's go have a look, shall we?"

Tilting her head, Emma got up and followed Rumplestiltskin down a corridor to Regina's room. Entering, she moved over to a wooden closet. She opened it, revealing a small rectangular box. She opened it, revealing the Dark one dagger – her name engraved on it.

"So, that's where it's coming from. Your dagger," Rumplestiltskin continued. "Since Regina left it in her room, I say finders keepers."

Emma reached forward to take the dagger, but a magical forcefield stopped her, and it nearly through her back against the far wall. "So, she put a spell over it. That's nothing for you, dearie. Shatter it. Shatter the spell and reclaim what is rightfully yours."

Emma shook her head. "I can't."

"Of course, you can. It's calling to its other half."

"Leave me alone!" Emma snapped.

"You know your friends cannot protect you."

"Stop!"

"You're the Saviour. Save yourself before it is too late."

"Get out of my head!" Emma snapped again, turning around to look at the figure of Rumplestiltskin. Raising her arms, she blasted magic at him. But it went straight through him. The formation of Rumplestiltskin disappeared, revealing only Hook standing in the doorway.

"Calm down," Hook told Emma. "There's no one here. It's just us. You and me." Leaning closer to Emma, he hugged her.

Emma hugged him back. "He's inside my head. I can't get him out," she said, noticing that the figure of Rumplestiltskin appeared behind Hook again. She eyed him. "He's here. He's always here."

Hook guided Emma over to the empty bed before getting the others. They came back to find that Emma was still there. Hook breathed a sigh of relief.

"What happened to her?" Mary Margaret asked.

"I have no idea. She hasn't said a word."

"It's getting worse, isn't it?" David asked as he entered the room.

Mary Margaret turned around. "David. Where have you been? I was looking all over the castle for you."

"With Arthur," David whispered. "It turns out he might have a way to help Emma. If we gave him the dagger…."

However, the Doctor had walked past the open door when he heard what David had said, and he gestured for them to come outside the room into the hallway. "You two. Out here."

Mary Margaret and David followed the Doctor out into the hall. "Doctor. What's wrong?" David asked.

"We can't trust Arthur," the Doctor said. "And we can't certainly give him the dagger."

"What are you talking about? Who told you that?"

"Oh, I think you know. Lancelot."

"Lancelot?" Mary Margaret asked. She hadn't seen her friend in a long time.

"Lancelot is dead," David added.

"Of course, he isn't," the Doctor said. "He faked his death to outsmart Cora. But enough about that. All that matters is that he's back and trying to help us. To help you."

"If he's trying to help us, where has he been all these years?" David asked.

"He never said. Honestly, it wasn't brought up."

"Are you sure we can trust him? He did go after Arthur's wife."

"You should know by now that everyone's stories are not what they seem," the Doctor said.

"When has the Doctor ever been wrong?" Mary Margaret asked her husband. "He was right about Neal back in Neverland. He'll be right about Lancelot. And we can trust him. He's our oldest friend. He married us."

"But that was a long time ago," David pointed out. "And now, all of a sudden, he's back. Why? Why's he back?"

"I don't know," the Doctor answered. "He never said."

"Look, Arthur is already for the dagger. If we come clean now, he can still help us."

Mary Margaret tilted her head. "So that's what this is about. You haven't met a king in a while, and you're star-struck."

"That's not what this is about. Our daughter is sick. We have to help her."

"So why become a Knight of the Round Table? How does that help her? Or is it that you need to feel like a hero again?"

"Maybe the Round Table is exactly where I should be."

"I'm sorry, David. But I agree with the Doctor. We aren't telling Arthur anything until we know we can trust him."

An hour later, David found King Arthur still in the room of the round table. Hearing the door open, King Arthur looked up. "David?" he asked.

David shut the wooden doors behind him. "We need to talk," he said, approaching where King Arthur stood. "Ever since we came to Camelot, we've been lying to you about why we're here. That stops right now. It's not easy for me to be here, and people I care about told me not to, but the Darkness is threatening someone I love, and I will do anything to destroy it. So, we're going to restore Excalibur. It's the only way we can save my daughter."

King Arthur tilted his head. "What does your daughter have to do with this?"

"Because she's the Dark One," David admitted. "We need to save her from the Darkness within."

King Arthur was silent for a moment, and he took a seat. So these outsiders had brought the Dark One inside the walls of Camelot? "I'm glad you told me about your daughter," he said. "Of course, I will help you defeat the Darkness inside her."

David sighed a breath of relief. "That is a relief. My wife and our friend thought this was a bad idea."

"What put them off me? It's the beard, isn't it?"

David shook his head. "Something a bit more serious. Lancelot. He's back."

King Arthur looked back at David. "Lancelot?" he breathed. "He's alive? And here in Camelot?" He couldn't believe it. "Serious news, indeed. Can we keep this between ourselves?"

David nodded. "Of course."

"Sometimes a husband has to go on the defensive. I wouldn't want my wife to learn that he's here."

As if hearing her name was mentioned, Guinevere entered the room. "She already has," she told them as she approached King Arthur's side. "Where is Lancelot?"

"He doesn't know, my love," King Arthur told her.

"Then tell me how to find him so I can make him pay for what he did."

"From what I heard, you both had some culpability in that."

Guinevere chuckled. "So you heard the old story? Believe me; the legend is only the beginning. Lancelot coveted far more than a kiss from a queen."

"I'm afraid my wife is right," King Arthur stated as he walked over to where his wife stood. "I didn't want to speak ill of a former knight – a former friend – but if Lancelot is in Camelot, that dagger isn't safe anywhere."

"Then it's a good thing I brought it with me," David said, taking a small rectangular box from his shoulder bag. Placing it on the table, he opened the box, revealing no dagger inside.

"Where is it?" King Arthur asked.

Meanwhile, Mary Margaret and the Doctor had left Camelot, walking down the dusty path. They came to a group of trees, exactly where Lancelot told the Doctor he would be meeting them, and they both looked around.

"You can come out now," the Doctor said. "It's only us."

Lancelot stepped out from behind the trees. "It's good to see you again," Mary Margaret stated.

Lancelot smiled. "And it's good to see you, too, Snow."

"We need your help," Mary Margaret said, as she took the dagger from behind her cloak, and showed it to her friend. "There's something we must hide."

The following day, while Hook was with Emma, trying to take her mind off the dagger, the Doctor, Mary Margaret and Lancelot set off through the Camelot woods. As they walked, Mary Margaret was catching up with her old friend.

"You know, you never told me what happened between you and Guinevere."

"It's complicated," Lancelot began. "But what happened is in the past. It doesn't matter anymore."

"It does if you still love her. Do you?"

Lancelot thought for a moment. "Yes. I'll forever love Guinevere."

They came to a clearing in the woods and approached a gold circle in the middle. "We're here," Lancelot told them.

The Doctor leaned forward and scanned the circle's surface with his sonic screwdriver. "The vault of the Dark One."

Lancelot nodded. "It is here that we will find what we're looking for," he said and began to press the sequence of correct symbols on the surface of the circle. The vault opened, and the three entered. They walked through a tunnel shaft before walking through a large wooden door, entering a leafy glade.

"This place," Mary Margaret commented. "I've been here before. I had a vision." Before Emma was born, she and David had sought to find answers about what their daughter would be like in the future. "I thought I understood what it meant, but maybe I was wrong. Maybe it was always about Emma becoming the Dark One."

"Visions and prophecies are never what they seem," the Doctor told them.

"What did you see?" Lancelot asked Mary Margaret.

"Emma crushed my heart. We have no time to waste. We have to make sure that Arthur can't get this dagger." Mary Margaret said, and she took the dagger from behind her cloak.

Lancelot gestured to the small altar behind him. "This altar is the place to secure it. But it's shielded by a nasty protection spell."

Mary Margaret sighed. "Well, if it's meant to keep the dagger safe, then maybe a person holding it can be allowed past?"

"Wait. It should be me."

Mary Margaret shook her head. "You've done enough."

"You need to let me do this, Snow," Lancelot told her, noticing how she looked at him. "What is it? Don't you trust me?"

Before anyone could answer, King Arthur, burst through the door behind them. "Apparently not," he said, brandishing his sword towards the three. "And that's a decision she's gonna regret."

"Arthur!" exclaimed Lancelot as he moved to stand in front of the Doctor and Mary Margaret.

King Arthur shook his head. "I wouldn't. Excalibur's blade is broken, but this one works just fine."

"You followed us here," the Doctor said. "Hoping to gain the dagger from us."

"I was right, then," Mary Margaret commented.

King Arthur glared at Mary Margaret. "Pity your husband didn't listen when you tried to warn him."

"Where is he?"

"Searching for you. In the wrong place. If you ever want to see him again, you'll hand over that dagger."

King Arthur glared at Mary Margaret, the Doctor and Lancelot. "Give me the dagger, or I will put this sword through my oldest friend," he said, moving the sword to point at Lancelot. "Like I should have done years ago."

"No," Lancelot told him.

"First, you try and steal my wife, and now you want to deny me the dagger after all I've done for it!"

The Doctor looked at Mary Margaret. "Give him the dagger," he said.

Mary Margaret looked back at the Time Lord. "What?" she asked. If King Arthur had the dagger, he could command – and maybe kill – her daughter.

"Just do as I say," the Doctor told her.

Mary Margaret nodded, giving King Arthur the dagger. "Here."

King Arthur snatched it from Mary Margaret. After years of searching for it, he couldn't believe he finally had the Dark One dagger. "I have waited a lifetime for this. Now I control your daughter. I can command her to reunite the sword and free Merlin. Excalibur's blade will be the last thing he sees before I use it to run him through. Then I will use the blade to snuff out the Darkness once and for all. I can become what no one thought I could … The greatest king in all the realms," he said, holding it in the air. "Dark One, I command you to appear!" he exclaimed, but nothing happened. Emma never showed. "I said I command you!"

"Emma's not coming," the Doctor stated. "Not today. Not ever."

"The dagger wasn't real?" Mary Margaret asked.

"Of course, it wasn't. I know a lot about that dagger and the Dark One," the Doctor began. "Well, I have to, since it belonged to one of my oldest friends. All I had to do was ask the TARDIS to make an exact replica. 3D printed, to be exact. And then I had to switch the fake dagger with the real one without anyone noticing. Why? Because I haven't been able to trust you," he pointed to King Arthur, "since we stepped foot in Camelot."

"And you knew he would follow us?" Lancelot asked.

"He wasn't the only one."

They looked behind to see David raising his sword at King Arthur.

"Took you long enough," the Doctor said.

"I had to keep my distance so Arthur wouldn't see me trailing him."

King Arthur stared at David. "You betrayed me. You broke the sacred trust of the Round Table."

"You tried to trick me with a catchy title and a comfy chair," David replied. "But my family is more important than anything you could ever offer."

"You don't understand. I'm trying to destroy the Darkness! I will save every realm. Including your home!"

David shook his head. "But the Darkness is in my daughter. So I fight to protect my family. And if that means betraying you, then so be it."

Lancelot looked over at everyone. "So this was all a show? Were you two even really fighting?"

"Oh, the fight was real," Mary Margaret answered.

"Oh, very real," David agreed.

"But we quickly realized that fighting wouldn't solve any problems. Especially when we were told we had a common enemy. We had to put Emma's well-being first."

The Doctor, David, Mary Margaret and Lancelot took King Arthur to an abandoned cottage not too far from the Vault of the Dark One. King Arthur was shackled in handcuffs while Mary Margaret looked over at Excalibur.

Meanwhile, David looked over at the handcuffs on King Arthur's wrists. "Why did you have a pair of handcuffs?" he asked the Doctor. "Where did you get them from?"

The Doctor turned to David. "How does anything get anywhere?" he asked back. "I gave up asking a long time ago."

Mary Margaret looked up from Excalibur. "What do we do with this sword?"

"Well, Arthur wanted to reunite it with the dagger and use it for evil. But that doesn't mean that we couldn't also use it for good," David told her.

Mary Margaret turned to David. "Like helping Emma."

"We can talk more about it as soon as we get back to Camelot and put someone worthy in charge."

"I spent a lifetime putting my faith in a false king. Camelot's true leader is its queen, Guinevere."

The Doctor eyed King Arthur, raising an eyebrow. "Is it me, or is he quieter than usual?" he asked before he heard a horse whinny outside. He walked over to a window and peered through it. "Because he's up to something." Outside, a group of King Arthur's knights surrounded the hut. Two knights approached the door and broke it down before entering, followed by Guinevere.

"Guin," Lancelot said, looking straight at her. It had been years since he last saw her face.

She turned to King Arthur, who got up and held his cuffed hands to her. Then, she began to pick apart the locks of the handcuffs.

"What's going on?" Lancelot asked. "Why are you doing this?"

"I love him," Guinevere said to Lancelot about King Arthur.

"No," Lancelot said, knowing what must have happened. "It's not real, you know. He must have used the Sands of Avalon on you. But, Guinevere, we can break this spell." They were true love, after all.

"Not interested," Guinevere told him as she took back Excalibur. She gestured to the knights. "Take this traitor to the dungeon where he belongs."

The knights dragged Lancelot out of the cottage, letting him watch in sadness as Guinevere kissed Arthur.

King Arthur turned to face Mary Margaret and David. "You're not the only couple with hearts that beat as one."

"The second you lock us up, our friends will know something's wrong, and your secret will be out," David said, drawing his sword.

"Who said we're locking you up?" Guinevere asked. "We're hoping the three of you can help."

"We will never help you," the Doctor told them.

"I'm quite optimistic that you will," King Arthur stated. "Guinevere. Fix this, my love."

Guinevere walked toward the three and blew the Sands of Avalon over them. However, when the sand touched the Doctor, golden energy flickered over his eyes.

The Doctor looked over at King Arthur and Guinevere. Then he looked over at David and Mary Margaret, watching as they relaxed their guard. "No, no, no, no," he said. Then, finally, the Doctor turned back to King Arthur and Guinevere. "What did you do to them?"

"The same thing should have happened to you," Guinevere answered. "Why weren't you affected?"

"Oh, maybe it's because I'm a Time Lord. We are one of the oldest and most powerful civilisations out there in the universe. So powerful, in fact, that Rassilon made safeguards within our DNA so we could never be simple slaves to do others' bidding."

King Arthur pointed Excalibur at the Doctor. "Arrest him," he told his guards.

The Doctor stepped back. He took his sonic screwdriver out of his pocket. "Actually, I think I might just arrest myself."

"And how will you do that?" King Arthur asked.

"By doing this," the Doctor said, giving his sonic screwdriver a whir. Seconds later, the TARDIS began to materialise around the Doctor. Once the TARDIS had fully materialised, the Doctor pressed the microphone button on the speaker. "I will stop whatever it is you are doing, Arthur. You have my word," the Doctor said, his voice echoing around the room of the cottage.

He turned off the microphone before dematerialising the TARDIS away.