The moment Chief Yagami and Aizawa found Light and C, L worked swiftly to ensure a general announcement was made to inform the hospital alarm was tripped as a prank. The group disappeared from the crowd as all returned inside. Apart from inquiring if Light and C were all right, L only demanded they return instantly to HQ. By the time the 'borrowed' Rolls Royce and Aizawa's car pulled up in the underground parking of the massive building, most of L's anxiety had wavered. Yet two potent emotions remained in turmoil within him. In the presence of others, he could show only one.

"Mr. Aizawa, if you would be so kind to rejoin Mr. Mogi and Matsuda to aid them with their research. Mr. Yagami, please take Light to the main office and monitor him. I will be there shortly. First, I must have a word with my colleague."

They all looked at C, but she kept her eyes on the ground, avoiding their gaze. Her silence angered L further. Though, in all honesty, any sarcastic remark or scoff she would've usually offered would undoubtedly have had the same effect.
As the trio walked to the elevator, L noticed Light glancing back over his shoulder. His expression was one of worry yet also intrigue. That didn't bode well. If Light Yagami, the number one suspect in the Kira-case, had witnessed something nobody should have ever seen, the danger to everyone living in HQ had exceedingly grown.

L waited until he was alone with C (though he was certain Watari would follow everything on the security feed). The light directly above her flickered, as if reacting to the dark entity her body inhabited. Yet the shadows on the walls and ground were stagnant. Last time it went wrong, they were dancing, obscure tendrils beckoning to surrender to their mistress.

"What happened?" asked L, keeping his voice in check.

"Nothing," answered C with a brief shake of her head.

"Please don't lie to me." It became exceedingly more difficult for the raven-haired detective to maintain his composure.

"Nothing happened. I regained control before she could claim her victim."

"Did anyone see? Yagami?"

"Yes, but he believes a ghost took possession of me."

"Are you certain?"

"He knows nothing, L. I told him before we went in that hospitals weren't a good place for me, so there's no reason for him to think something other than that happened."

"Very well. I'll make sure he continues to believe that. Please go upstairs to the room now."

"L, I —"

"Don't."

Regarding social convention, L was almost the same as C. For he, too, only apologized when he deemed it necessary based on the reactions of others around him. The difference was that, on the odd occasion such as towards Watari, for example, he meant his apology. C never did. She was incapable of it.
So he shut her down. He refused to hear another empty 'I'm sorry' from C. All the anger he'd been trying so hard to keep down would surely come out then. Anger born from the physical hurt she caused him, from acting so rashly, from endangering others. Words meant for C would echo through to Cassandra. And she had no fault in any of this. 

"There's a recording of my conversation with Light," said C then. "We didn't speak of Kira, but there may still be something there than can help... you."

"I'll listen to it later. Once more, please go away."

She finally looked up at him, and L gasped quietly at her expression. Was that... guilt? Or shame? He couldn't tell. It wasn't something she had shown before. Not when she was in control, anyway. Though trapped in the same body, C was the exact opposite of Cassandra. One was bold, aloof, and always so sure of herself, while the other was caring yet demure and frightened of everything around her. Their expressions never mixed. But right now, in the aftermath of what could have been a lethal mistake, the persona who only lived thanks to the fragmented mind of a severely traumatized twenty-four-year-old appeared stricken and rendered to emotions engrained in every decent human being of which she had no real understanding of. It unnerved L. He looked away, remaining perfectly still as C walked past him. Not once did she even try to get his attention again. Her footsteps receded, and the elevator closed, leaving the young detective alone in the underground parking. 

L crouched down, thumb pressed against his lower lip, and counted to a hundred to calm himself. It was enough time for the elevator to carry C up and come back for him. When he entered, he meant to push the floor to where the main office was located. Instead, his index finger touched the button to go up to the same floor C had.
L groaned, realizing his mistake only after the elevator had gone all the way up. He moved to push the correct button but froze upon seeing the open door to his room at the end of the corridor. Had C expected L to follow her? Or was it... her? 

"C?" 

L waited for the reply that never came. Slowly, he walked toward the room and entered. The soft sobs he heard made him stop dead in his tracks. A figure lay curled up on the ground in front of the bed.

"Cassandra." L's body moved on its own. Within seconds, he sat at her side and held her close. "Ssh, it's all right. You're safe."

Cassandra buried her tear-stained face against his chest as she desperately clutched L's shirt. He was no good at offering words of comfort, so he did the only thing that always seemed to work — he stroked her hair. 

"S-She's back, isn't she?" he heard Cassandra ask in a tiny voice.

"Yes, I'm afraid so."

"Why? It's b-been nearly two years. W-Why now?"

"I wish I knew."

"Lawliet, please... promise me." 

L froze. Not that again. Anything but that. He drew back and cupped her face to make her look at him. There was so much suffering in her eyes. So much agony. It pained him to see her like this again.

"I promise," he whispered.

A strangled sigh of relief escaped Cassandra. He brushed his thumb against her cheek. She slowly relaxed at his caress, and after a few minutes, her eyes fell shut. L carefully picked Cassandra up and carried her to bed. It was only then he noticed she yet fisted his shirt. Left with no other choice, L alerted Watari with a text message to say he'd come down later and lay beside her. 
With the feeling of a comfortable bed underneath him, and Cassandra's warmth so close to him, L's fatigue got the better of him. As his eyes closed, the memory of his first meeting with the red-head drifted through his subconscious, melting together with the promise he made. Had he known back then what lived inside Cassandra, before their relation grew into what it was today... he would have killed her without a moment's thought. 

📓💀📓

Five years ago - February 14, 2002

"Is this seat taken?"

The most peculiar eyes L had ever seen peered up at him. One blue, one hazel. He was awestruck by them. Awestruck, and intrigued. What were the odds that the person of interest in this unusual case had an equally unusual genetic mutation?

"Y-You want to sit... here? With m-me?" inquired the girl on the brown couch with a trembling voice. 

"Yes, is that okay?" L held her gaze.

"Um... y-yeah, sure."

"Thank you." He sat next to her, putting his teacup on the coffee table, and introduced himself with his alias. "My name is Damian."

"C-Cassandra." 

"That's a pretty name. Nice to meet you, Cassandra."

L offered a smile, to which Cassandra hurriedly averted to look back out the window. He cocked his head. Maybe he shouldn't have tried to smile yet. He knew he wasn't very good at it, and his attempt must've spooked her. Either that or she was really this good of an actress. 
The silence between them gave L a chance to look at Cassandra properly. Her hair came to her shoulders and looked like it hadn't been washed in a while. She wasn't wearing any make-up, but in a place like the Glass House, that wasn't uncommon to see. The oversized gray sweater with the clinic's logo on the left shoulder was stretched over her pulled-up knees, so only her white socks were visible. Judging from her slender ankles and wrists, she had to have a lithe figure. 

The file the doctors provided us mentioned she doesn't eat that much. A minimum at breakfast, lunch, and dinner, and only an occasional red apple in between.

His eyes narrowed when he then noticed the fingers of her right hand, stained with a variety of colors from a felt pan or possibly crayon, tapping against her knee in a quaint cadence. A silent gasp fell from his lips as he realized this was something piano players did, often subconsciously. 

Judging from her hands alone, I believe I can safely deduct she's an artist, mused L. Curious. That wasn't in her records. Neither was her last name. Out of security, perhaps? Or was it a calculated decision? Regardless, I'll add this to our current profile of her. Maybe she's known in certain circles. 

He subtly mimicked her, making sure she didn't see. It took a few seconds, but a melancholy, yet vivid tune started playing in his mind then. L stilled his movements. It couldn't be. 

"Extraordinary," he muttered. 

"What?" Cassandra turned her attention back to him. 

"The song you're playing against your knee. If I'm not mistaken, it's Saint-Saens' Danse Macabre."

The young woman raised a brow. "How did you —?"

"I play as well. And I must say, I rarely come across other pianists who take on a song usually played with mainly strings, wind instruments and percussion. It's not an easy one to perform without the support of, at the very least, a violin. Where did you learn?"

Cassandra offered no reply. She just gawked at him, the setting sun lighting up her dual eyes with a haunting gleam. The longer the silence between them lingered, the more L became aware of her. After a week of surveillance in the Glass House, he'd concluded the nineteen-year-old who kept to herself yet somehow inexplicably caused the most trouble had to at least have some knowledge of the murders. When he eventually decided to engage her directly and actively go undercover himself — something he'd never done before, and much to Watari's disapproval — he still held some reservations. Yet now that he was this close, he was certain of it — behind Cassandra's apparent apprehension slumbered a cunning murderer. One he would bring to justice, even if it killed him. 

"Did I say something wrong?" asked L after a few minutes. 

"N-No," said Cassandra hurriedly. "It's just... you're the first one to acknowledge my tic for what it is. And you recognized the song merely by looking at me. That's... amazing."

Hm, odd, thought L. Despite supposedly being English, I don't detect even a hint of an accent. She's constantly surrounded by others speaking that dialect, so she can't possibly have outgrown it. Is she purposely hiding it?

"I'm just observant," he said with a light shrug. "Can never be too careful, right?"

Cassandra pressed her lips together. She finally lowered her gaze. L meant to press on his previous question, but an angry scream from the other side of the room distracted him. He watched as two nurses hurried to an elderly man yelling at nobody in particular. They coaxed him away before his behavior could disturb any of the other patients. When L turned back to his suspect, he had to blink twice to make sure it was still the person. 
In less than five seconds, the young woman he'd been talking to underwent a metamorphosis. She'd put her hair up in a bun with a rubber band and was no longer seated with her knees pulled up to her chest, but leaning back, one knee over the other and arms crossed over her chest. Despite every inch of her face now showing, a dark shadow crossed her features. And even though she was seated away from the light, the carmine hues from the sunset yet reflected in her calculating eyes.

"What do you want?" she demanded.

"Want?" L feigned confusion. "What do you mean?"

"Don't play coy with me, pretty boy. You're not the only one who's observant. In the twenty-four hours you've been here, you haven't spoken to a single other patient here. Hell, you don't even talk to the staff, unless it's to thank them for bringing you tea and sweets."

Pretty boy?

"You don't talk to anyone either."

"Which you would know, of course, since you've been following me everywhere I go."

"This is a small clinic," rebuffed L. "There aren't many places to go on one's own except the garden, common room, and our patient rooms. You see me now because I am new here and offer a change in your regular surrounding."

"Is that what you said to your other stalker victims to convince them they were imagining things?"

"I'm... a stalker?"

"If the shoe fits. And sit straight, for God's sake! You're going to keel over and hit the coffee table if you keep sitting that way."

L was perplexed. No one, not even Watari, had ever spoken to him in such a manner. He didn't know what to make of it, but he sure grew more intrigued by the minute. Cassandra's shyness and anxiety were completely gone. She confronted him without stuttering, and with a much stronger voice. If he hadn't been sitting right beside her, he would've assumed she switched places with someone who bore an uncanny resemblance to her. But there was only one entrance to the little sunroom, and they'd been alone the entire time. This was Cassandra, and yet... it wasn't.

"Listen," she leaned in, "I don't know what your game is, but I don't want to play. I'll ask nicely because you're new here and don't know the ropes yet — please don't come near me again."

Cassandra's glare penetrated L's being. It caused the most unsettling sensation he ever experienced, but he couldn't bring himself to look away. He was utterly mesmerized. Prompted by the urge to find out how far she'd take this, L asked, "Or what?"

The tension grew. Time slowed further with every beat of his heart, and then... L barely had time to register the cat-like pounce. He smacked against the ground on his side, falling right between the couch and the coffee table. Cassandra quickly turned him on his back and straddled him. Her nails dug into his throat, cutting off his breath. 
Cassandra lowered herself to him until the tip of their noses touched. Looking into her eyes then, L felt cold. Paralyzed, even. He hadn't felt like this since... November 1990. But he wasn't an eight-year-old boy anymore. He was almost eighteen, and already a world-renowned detective. He wouldn't make the same mistakes. This time, he would fight.
L gripped Cassandra's wrist with both hands to pry her off, but she wouldn't relent. The force Cassandra held him down with was phenomenal, and not at all what he would've expected from someone who'd appeared as frail as her. 

"Consider this your only warning," she hissed. "Leave. Us. Alone."

Three male nurses burst into the sunroom and pulled Cassandra off L. He coughed and gasped for much-needed air. A pair of wrinkly hands gripped L by the shoulders and helped him sit back on the couch. It took him a moment to recognize Watari. His guardian and butler had only allowed L to go into the lion's den on the condition he, too, went undercover. Watari's real-life credentials in studies of psychology were enough to secure him a position. 

"Are you all right?" he asked L, concerned. 

The latter merely nodded. All his attention was on the girl being carried away by the nurses as if she were a criminal. She was a criminal. L knew he'd found his murderer. But instead of taking action, he remained silent. He couldn't end things just yet. Not when he still didn't have a single answer. In fact, he only had more questions. 

Who was Cassandra?

Why was Cassandra here? 

What had happened to Cassandra? 

How had Cassandra subdued him so quickly and with such force? 

But perhaps most importantly — what did Cassandra mean when she said 'us'?