"Remind me again why we're fighting Hawk Moth, m'lady?" Cat Noir was standing on the banks of the Seine River next to his partner, preparing for the biggest challenge they had faced yet.
"He's tired of losing. I suppose he thinks if you want something done right, you have to do it yourself." Although she didn't show it, Cat Noir could tell that Ladybug was nervous. "Hawk Moth could be preparing anything, Cat Noir. We have to be ready for whatever we are facing."
Thump. A noise was heard behind the duo. Ladybug swiveled and came face to face with Paris' biggest fear: Hawk Moth.
"Ready to do battle, kids?" Hawk Moth sounded even more menacing standing right in front of them. Ladybug caught her kitty's eye and flashed a wink in his direction. By the way his face lit up, Cat could tell that she was ready, and so was he.
"Ready."
An hour later, the three of them were still fighting. Neither side had a clear advantage, but they had destroyed half of Paris as they went along. Now, they were back to where they had started. By the Seine River. Cat Noir was still saving his Cataclysm for an emergency, but Ladybug had called upon her Lucky Charm.
Beep. Beep. Her earrings flashed in warning.
"I only have three minutes, Cat! We have to act fast!"
"Should I use my power?"
"No, Cat. You might need it for an emergency." Ladybug warned. The Lucky Charm hadn't been very useful. It had supplied them with a replica of the Butterfly Miraculous, and Ladybug had been very cryptic about what to use it for.
We have to go back to the Seine. Cat Noir was confused by her instructions, but they did so. However, she hadn't used it yet, and she was running out of time.
Beep. Beep.
"Two minutes." Ladybug whispered, voice laced with concern.
"Go. I'll hold off Hawk Moth while you transform back."
"No, Cat. We both know that neither one of us can face Hawk Moth alone. We're a duo, and it's going to stay that way if I have to fight as a civilian." Cat Noir wanted to protest, but he knew it wasn't going to do any good, so he kept his mouth shut.
"Soon it will be down to just the two of us, Cat Noir." Hawk Moth's voice broke the silence by telling Cat something he already knew.
"Don't worry. I'm sure m'lady has a plan. I trust her completely." Cat Noir spoke with as much determination as he could muster.
Beep. Beep.
"M'lady, you only have one minute left!"
"I know. But I can't leave now. We'll cross that bridge when we come to it. Ah! Bridge! Now I know how to use my Lucky- Hey!" Ladybug was cut off by Hawk Moth restraining her on a bridge above the water of the Seine.
"Very soon, you'll detransform, and I'll have your Miraculous."
Beep. Beep. Ladybug's last spot began to flash. She wiggled an arm free and gave Hawk Moth a punch to the gut, causing him to release her.
"M'lady!"
"Grab on!" Ladybug, desperate, threw her yo-yo out for Cat Noir to grab it as she fell off the side of the bridge, but her transformation dropped, and there was nothing she or Cat Noir to do about it.
"Ladybug!" Cat Noir screamed. Then, unable to force himself to look away, he got a clear image of his lady's civilian form hitting the water. Even in the dark of the night, she was unmistakable. "M-Marinette?" He spoke in a voice that was barely a whisper. He had to save her. He tried to jump-
"I've got you now, Cat Noir. Give me your Miraculous!" Hawk Moth restrained him in the same way he had held Ladybug.
Cat Noir was furious. "Cataclysm!" He shouted it as loud as he could, just to make sure Hawk Moth could hear. Then, without hesitation, he swung his arm backwards and made contact with the arm of the villain that was keeping him from Marinette.
"AAH!" Hawk Moth screamed as the Cat's destructive energy took him over, leaving nothing but ash.
Cat growled. "No one hurts my lady." He dove into the deep, murky water and recovered Marinette, bringing her to the surface. Even through his costume, the cold water bit at his skin, freezing him. "Marinette?" She rolled over and began to cough up water as Cat Noir looked out over the city.
Without the Miraculous cure, Paris would be in ruins. Hawk Moth would stay destroyed, and Marinette would stay sick. The Butterfly Miraculous would never return. It would be lost forever. That wouldn't be easy to explain to Master Fu.
Cat Noir sat with Marinette by the banks of the Seine for hours as she slowly regained consciousness in his arms.
"I guess that's it, huh?" Cat barely heard Marinette's voice. "Tikki, spots on!"
"M'lady? Why are you transformed? We need to get you to a hospital!"
Weakly, she countered, "My Miraculous cure will fix everything." Grabbing the replica of the Butterfly Miraculous, she shouted the words that Cat Noir loved to hear. The words that meant that they had defeated another villain. "Miraculous Ladybug!"
Soon enough, everything was back to normal. Hawk Moth reappeared and renounced his Miraculous, leaving Gabriel Agreste in his place. Cat Noir revealed his identity to Ladybug and to Hawk Moth. Now, all detransformed and standing on the banks of the Seine, stood a princess and her knight, a father and a son, and three people whose lives were forever changed by the supernatural things they couldn't control.
Rather than explaining everything that happened, I'll tell the short version: The Peacock and Butterfly Miraculouses were both recovered and sent back to the Master, Hawk Moth was thrown in jail, and as for Marinette and Adrien? I'll leave that to your imagination.