A/N: Inspired by a terrible lovely heartbreaking post by sheriffswan on Tumblr - thanks for letting me write it!

Emma skidded to a halt in the elevator, bracing herself against the iron bars at the back. She was still turning around to demand what was taking everyone so long when David and Elsa joined her. Belle stayed put, already reaching for the controls. She looked distraught, her eyes red and her cheeks wet, but her chin was raised and she gave Emma a nod before shutting the door. With a shudder, the rickety contraption began its descent.

Emma used the time to catch her breath and double-check her gun. Beside her, David stood ready, sword in hand, jaw set in familiar determination. She couldn't help thinking back to her first time using this death trap, when Regina had lowered her down to fight Maleficent. She'd been the one to carry David's sword, back then.

It felt like a lifetime ago.

And here she was once again, with a life hanging in the balance. Once again, with Gold's betrayal making her heart pound and her fists itch.

She gripped her gun. He was not taking Killian from her. He was not.

"Do we have a plan?" Elsa asked.

David let out a tense breath. "We don't even know what we're up against."

"Killian, for one," Emma said, relieved when her voice came out almost steady. "Gold has his heart, so he can control him. We need to be ready for that."

"If it comes to that, I'll hold him off," David told her. "You two just concentrate on getting his heart back."

"Right." Emma pressed her lips together, looked up at him again. She didn't like the idea of that duel, not one bit, but David was a skilled swordsman and Killian didn't have magic to give him an advantage. And she liked the other options she'd come up with even less. This entire situation was one hell of a mess. "Just... be careful."

"Always," he assured her. The lift came to a ponderous stop, and David heaved the door open. "I—"

Elsa looked worried. "What's that?"

Now that the noise of the elevator had died down, Emma heard it, too: thumping and banging not too far away, echoing along the tunnel, punctuated by the occasional shriek.

"Guess Belle was right about Maleficent," Elsa commented.

"They're trying to trap her in the hat." David shook his head. "I never thought I'd try to save her life, but I guess there's a first time for everything."

You never forget your first. Emma's heart gave a painful little lurch. She clenched her jaw and nodded. "Come on."

With the sounds of the battle raging up ahead covering any noise they themselves made, they jogged along the tunnel, Emma leading the way.

When she reached the cavern entrance, she stopped, gesturing for the others to do likewise. Gold stood directly ahead of her, focused up towards Maleficent in her dragon form. She was twisting and turning mid-air, caught in what looked like a net made of golden and purple light. In contrast, Gold was completely still. He had an object in each hand – his right held the Dark One's dagger aloft, his left was closed around a stocky cylinder that Emma recognised from Belle's description. The hat. Belle had been right. He was trying to send Maleficent into the hat.

And – Emma's eyes landed on a small chest at Gold's feet. It was open, and something lay within it, something that glowed with a ruby-red light. Killian's heart.

Killian himself was on the ground, bloodied and bruised but still moving. He was in the process of levering himself up on his arms, grimacing and twisting his neck to glare up first at the dragon, then at Gold. Emma almost took a step back when she saw his expression, which was nothing short of murderous.

A sentiment they could agree on.

Gold lowered the dagger and switched his attention to the hat-cylinder, and Emma reacted on instinct. "Gold!" she yelled, and stepped out into the cavern.

At first, Killian thought he'd imagined the voice, but as he whipped his head towards the sound, his eyes confirmed it. If he'd still had his heart, it would have sunk down to his toes. "No," he breathed. What the bloody hell did she think she was doing?

"Ah, Miss Swan," Gold called out, still focused on Maleficent. "And the cavalry, if I'm not mistaken. So good of you to join us. That's your cue, Captain."

Killian's eyes were still on Emma, who stood firm, looking as determined and fierce as he'd ever seen her. Normally, the sight would have filled him with pride, but all he felt now was dread. There was no compulsion, not yet, but the crocodile clearly had no interest in being distracted by a fight with the Saviour. He'd make Killian do it, and this time there would be no play-acting, no putting on a show the way he had for Cora, no pretending to be knocked out of the fight.

And if he didn't kill her, she would be here to watch when Gold crushed his heart.

"Go to hell," he ground out.

"Oh no, I'm afraid that's your fate," Gold said, finally turning away from the dragon that Killian had lured into his magical net, satisfied that she wasn't going anywhere. He tucked his dagger away and reached down to retrieve Killian's heart. "But you have a job to do first."

Killian got to his feet, his body moving without his command and against his will, the sensation of being controlled making his gut churn with the wrongness of it all. He drew his sword and strode towards Emma, every step pounding in his ears. No, no, no...

David stepped in front of his daughter, sword raised. "You'll have to go through me."

Something that almost felt like relief flooded through him. The prince was a fair swordsman, by all accounts. He'd have a chance. Maybe he'd even win, and hopefully have enough sense to kill Killian before Gold could use his heart for his thrice-cursed spell.

He looked David in the eye, trying to apologise even as he felt his lips curl into a sneer. "Then that's what I'll do."

David nodded. "You'll try."

Killian lunged forward, a blow that David caught easily. The clash of metal rang in his ears, and his blood began to hum with the thrill of battle. David stayed defensive, and Killian used hook and sword to drive him back, trying to fight his way through to Emma.

She'd used the distraction to move, he noted, trying to circle around to Gold. He wanted to warn her, to yell at her, tell her to run and get out of here, but he couldn't turn his attention away from the battle. Besides which, he knew better than to think Emma Swan would run from a fight, hopeless as this one was.

David launched a counterattack, and Killian parried it with practiced movements, feet shuffling on the uneven ground.

"Sorry, dearie," Gold said somewhere behind him, and Killian spared another glance at Emma. She seemed to be stuck in place, held there by magic no doubt. "I'm afraid I can't allow you to interfere."

"Stop it, Gold!" Emma yelled. "You're insane! Do you know what you're doing? Belle's upstairs crying her eyes out because—"

"That's not your concern," Gold bit out. "I have to do this."

There was another clash as Killian caught David's sword in his hook, almost wresting it from the other man's grip. A stupid error; the prince was just as distracted by Gold and Emma as Killian was, but he didn't have that sickening compulsion in his chest that kept him fighting no matter what. Killian brought his own sword up. David twisted out of the way, but not before the blade connected. Fabric ripped, and a line of blood welled up on the prince's arm.

Killian choked back a sob.

No, no, no.

Light flashed to his left as Emma and Elsa's magic clashed with Gold's, but Killian didn't stop to watch the show. He pressed his advantage, driving David further back even as the dread inside him filled his limbs and his gut and the terrible, empty place in his chest. And he knew, right then, that if David didn't manage to rally his wits and his strength somehow, he was going to kill him.

The light turned golden, and he realised that Gold had thrown the hat onto the ground, ready to draw Maleficent into it.

"Stop!" Emma yelled. "I don't want a fight. Do what you want with the dagger, but let Killian go!"

"Oh no, I'm afraid Killian," Gold's voice curled around the name with a sneer, "is an important asset. In fact, this is his big moment."

Killian's chest exploded with pain, making him stagger, his sword dropping to the ground mid-parry as he clutched at the spot where his heart had been.

"Hook!" David reached out to steady him. Black spots danced at the edges of Killian's vision, but he could still see Emma, frozen in place a few meters away.

She was whirling around towards him, eyes wide. "Killian...!"

He heard an echo of his own voice in hers, that same note of desperation that he remembered from that cursed day on the Jolly Roger when he'd last seen the Dark One crush a heart. He caught sight of Gold standing a little further away, fingers curled around his heart, hatred twisting his face, and he realised that this was it. No hero's death for him, no brave last stand or blaze of glory, just one last act of betrayal. One last broken promise.

His chest hurt like blazes, twisting his features, and he curled forward, instinctively trying to protect the injured part of his body. He struggled to draw breath past the pain, his lungs feeling as if they were on fire.

It was nothing compared to the look on Emma's face. She looked horrified, shaking her head as she stared at him, a silent plea in her eyes.

I can't lose you too.

It was going to break her heart, he knew that now. He'd thought that he couldn't regret his deal more than he had already, but he'd been wrong. He'd been scared of losing her, selfishly worried that her feelings for him were not that strong, but he'd been wrong, and it made everything ten times worse. Gold had taken his greatest wish and turned it into a nightmare. Because she cared, and he'd been there. He'd been standing right where she stood now, unable to move, unable to do a damn thing except watch.

He should never have gone near her. He should never have tried to prove to her that he meant it, that he cared. Promises, nothing but promises, and all of them about to be broken.

He wanted to say he was sorry, tell her how much he loved her, but he knew that he didn't have much breath left, and he would not spend it on that. Milah's last words had haunted him for centuries, fuelled his thirst for vengeance. He could see the spark of it in Emma's eyes now, that darkness threatening to overtake her, and he would not, could not, let it.

"Don't," he forced out, his vision growing darker. Something hummed in his ears, growing steadily louder, and he could barely hear himself speak. But he kept his eyes on Emma's, and he tried to put everything he still felt into that look, knowing that she could read it. She'd always been able to read him. There was only one thing he needed her to hear. He'd let her down, broken his word, failed again, but he could still do one thing right. His legacy would not be one of revenge and darkness. Not for her. "No vengeance. Swan."

The world tried to slip away from him. He fought to hold onto it, but the darkness was creeping into him now, the noise in his ears reaching a crescendo. But he could still hear Emma's voice above it, panicked and fearful.

"No!"

He wanted to reassure her, tell her that it was okay, but the pain was taking over all of his senses, and he couldn't get any more words out.