Derek stared in momentary shock at the door of the now vacated on-call room. He felt nauseous and shaky and broken. He couldn't make sense of it. Why would Mark and Meredith be together in this room – a room with a bed? And why would Mark wrap his arms around her after they emerged?

Meredith had smiled. She had smiled at Mark with a genuine smile – a warm, happy smile that was typically reserved for him, not Mark.

He felt completely unnerved. Unnerved and enraged. His stomach tied itself in knots. His chest tightened. His skin burned.

This was his hospital. He was about to be chief. His hospital and his girlfriend and his ex-best friend, together…

The walls were closing in on him. He needed air. He needed space. He needed something.

He needed an explanation that could stifle his active imagination.

He skittered down the hall in the direction that Mark had gone, completely oblivious to everyone around him. He had a singular purpose and nothing could distract him now. He couldn't stand back and let this happen to him again. He couldn't let Mark take away everything he ever had.

How could he have been so blind?

Mark stood at the end of the hall flirting now with Cristina. The two smirked at each other and bantered, although Derek couldn't hear what they were saying yet. He could just tell what was happening from their body language.

Cristina noticed Derek coming towards them and pulled away from the conversation, scampering off to the stairs to avoid him.

She knew. Maybe she knew. Derek wondered how long something had been happening between Mark and Meredith. Certainly Meredith would have said something to Cristina. Cristina was her person.

Derek was furious. He clenched his fists and prepared to hurl them at Mark. This time, he would do more damage than before. Mark wouldn't be able to repair himself when Derek was done. He wound up and lunged at Mark.

"Jesus!" Mark yelled, holding his hands up to block the punch. "What the fuck?" He ducked, grabbed Derek's arms and pushed him away, shoving him against the wall. Derek crumpled at the impact, as if he had just collapsed onto a house of cards that couldn't break his fall, and he slouched to the floor.

"Seriously, Derek! You really need to fucking stop that. Use your words. Fuck! What is your problem?" Mark continued ranting, shocked.

"You…You're my problem…" Derek grumbled angrily.

Mark rolled his eyes. "And what have I done now?" He looked around to see who was near. Luckily this area of the hallway was pretty empty. He didn't think anyone had seen their encounter.

"You know what you did," Derek hissed through clenched teeth.

"No, really. I don't. Enlighten me," Mark retorted sarcastically. His friend looked pathetic. Pathetic and upset and broken, and Mark felt a little bad for him.

"What were you doing with Meredith?" Derek asked, accusations dripping from his strained voice.

"What?" Mark asked, trying to make sense of this. "Oh, I get it," he laughed. "You saw that."

"You're laughing?" Derek said, standing up rapidly – so rapidly the room swirled a little. "You're fucking laughing?"

"Yes, Derek. You're such a jackass. Seriously. Did you honestly think that Meredith and I hooked up in the on-call room? Seriously?"

Derek shook his head in frustration. "What were you doing?" He asked impatiently.

Mark looked at him sadly for a moment, realizing that he had caused his friend to react this way. For Derek, it must have been easy to jump to this conclusion. After all, he had trusted Mark and Addison together until he found them having sex. He'd been completely oblivious until that point, and then his world came crashing down in the aftershocks of one tremendous tidal wave. Mark was the one who had broken his friend, and he wondered if he'd ever be able to restore Derek's trust.

"She was upset about you and some stupid fight you had. I reminded her that you've become this overprotective territorial prick because you love her so much, and I encouraged her to take it easy on you because you've clearly lost your mind," Mark insisted.

Derek's body relaxed a little, and he sunk into an embarrassed slouch, unable to meet Mark's eyes. Of course they hadn't slept together. Meredith wouldn't ever do that to him. Mark, maybe. But, Meredith? Definitely not. Even at her angriest, she wouldn't go there. Not with Mark. "I'm sorry," he whispered.

Mark sighed. "I know you may not ever trust me again – not really – but you have to know, I would never do anything to come between you and Meredith. You probably thought that about Addison, too, but really, man. This is different. I loved Addison when you had already stopped. But you and Meredith…you love each other so much…I couldn't come between you if I wanted to," he urged. "Well, I mean, all women succumb to my charm eventually, but Meredith hasn't given in as easily as most."

Derek nodded, still staring at the floor.

"You two are the only friends that I have here. Please don't be mad at me for trying to keep you together," Mark pouted teasingly.

Derek looked up and smiled weakly. "I'm not mad. Stupid, maybe, but not mad."

"Yeah, you are a bit of a dumb ass sometimes," Mark joked.

"Thanks."

"You just need to learn to trust each other. You're getting there," Mark encouraged.

"Yeah. You're absolutely right. I should know better than to think you'd stand any shot with her. She has much better taste in men," Derek chided. His weak smile slowly upgraded itself to a full grin.

"Warped taste, maybe. Certainly not better," Mark said cockily. "We'll talk later?"

Derek nodded.

"Oh, and Derek? You need to work out man. Your right hook is not up to par. Until then, words, not fists, okay? I'd hate to see you get your ass kicked in a fight you initiated," Mark teased as he walked backwards down the hall.

Derek laughed a little and set off back towards his office. He was much safer there - less likely to run into anyone or see things he wasn't expecting. There was a much smaller chance of overreacting to stupid things if he just hid in there for awhile. He felt like he was losing his mind today, and at least in there, no one would be a witness.

"You didn't come home last night," Cristina accused Meredith as she stood next to her in the basement, basking in the glow of the vending machine. She punched the buttons aggressively, making Meredith feel a little more flustered in an already frustrating day.

"Um, no, I spent the night with Derek," Meredith said, annoyed. "Did I need to call home for permission?"

"Do what you want, Mere," Cristina replied sarcastically.

"What's your deal? Why are you so pissy?" Meredith asked. Her face was pinched a little in aggravation.

"Nothing. I just wondered where you were last night," Cristina retorted.

"Bullshit. You knew where I was. What's wrong?"

"I just…I think you need to be careful," Cristina said suspiciously.

"I'm fine. We're happy. We're working things out. Really."

"Yeah, sure. I'm happy for you," Cristina said dismissively.

"This isn't about you," Meredith snapped. "And don't pretend to be happy when you're clearly pissed that I got back together with him. I don't know why you continue to be so negative about us. He never did anything to you."

"No, but he did to you…"

"And if I can forgive him for that and be happy, you should be, too. For me. Be happy for me, because he makes me happy. And damn it, I deserve happy!" Meredith ranted. "Last week you were encouraging me to be with him, and now this week? This? What the hell?"

"Okay, okay. Sorry. I'm just…stressed," Cristina sighed.

"Is it Burke?" Meredith asked softly.

"Of course not, I'm over him," Cristina sneered.

Meredith rolled her eyes. "Yeah, I know. That year of your life and the man you nearly married are unimportant. So what's really bothering you, Cris?"

"I'm just stressing about the whole apartment thing. Especially now that you and McDreamy are clamoring to get your bed back," Cristina confessed.

"You'll figure it out. You're Cristina Yang. Cristina Yang solves her problems quickly," Meredith dismissed. She was in no mood to host a pity party today.

"Yeah, I know. Of course I will…" Cristina said, trying not to reflect her disappointment on her face.

Meredith read her friend's reluctance immediately, but decided not to acknowledge it. Cristina couldn't find a place because she didn't want to. She wanted to be around people right now, and the people in Meredith's house were her family. They were the ones that could take care of Cristina and help her repair what Burke had broken. Cris would never admit that, but Meredith knew that was how she felt. Meredith felt a little guilty for insisting that Cristina leave under those circumstances, but she really did want her space back. She wanted a space for her and Derek and no one else, person or not.

"I'll keep looking for you, too, and we'll figure this out later, okay?" Meredith reassured. "I need to get back."

Cristina nodded.

Meredith crumpled her nearly empty potato chip bag and tossed it in the trash. She didn't really need to leave, but she needed to get away from Cristina and all of the negativity for a while. She was trying so hard to be more bright and shiny today, especially after her conversation with Mark, and she knew that Cristina might bring her down.

She wandered over to the elevator and got in. The hospital was quieter than normal even for a Sunday night, and the elevator was completely empty. She instinctively pushed the button to the floor with Derek's office on it. She wanted to see him and discuss their fight earlier. She felt guilty about how she had left things, and she hoped that he hadn't gone home for the night already.

The hall was empty but for the lights peeking out from his office. It wasn't surprising – attendings that were there on a Sunday night were unlikely to be in their offices. But Derek wasn't typical of the attendings, and she was relieved to see that he was still there.

She opened his door and watched as he stared at his computer screen, typing steadily on the keyboard in front of him. He was surrounded by notes and papers, and the glow of the LCD reflected in his blue eyes. His concentration was so deep that he didn't even look up as she entered.

Meredith hovered in the door a moment, watching him. She smiled as she began timing how long it would take for him to notice her there. She enjoyed watching him work, whether it was in the OR or elsewhere. His focus was often unwavering, and she knew it was one of his strengths as a neurosurgeon.

"Hey," she finally whispered, growing impatient to be discovered.

Derek did a double take at the figure standing in his doorway. He wondered how long she had been standing there.

"Hey," he smiled back, leaning back away from his computer to focus exclusively on her.

"What are you working on?" Meredith asked casually. She closed the door and walked around behind Derek's desk so she could massage his shoulders. He felt tense and stiff, and her nimble fingers quickly sought out the knots in his shoulder blades.

Derek sighed as he felt the tension evacuating his body at her touch. He could sense from her movements and body language that things were better between them – that she had calmed down substantially from the afternoon. "I'm just finishing a research paper for a conference I'm attending in a few weeks."

"Ah…interesting stuff?" Meredith asked, using both hands to knead one particular spot.

"Pretty dry, I think. I'll let you read it when I'm done if you want," Derek replied.

"Wow, with a recommendation like that…" she joked.

He smiled and reached up for her hands behind him, telling her she could stop. He spun his chair around so he could look at her while he continued to keep her hands in his grasp.

"Mere, about earlier…" he started.

"No, stop. I'm sorry, Derek. I know you weren't trying to meddle. You're allowed to be upset at Thatcher. You were just looking out for me," Meredith acknowledged.

Derek looked up at her, his eyes searching hers.

"You don't need to tackle all of these problems on your own, you know," Derek voiced. His hands rubbed Meredith's delicately.

"And you don't need to solve them for me," Meredith retorted.

"I know, it's just…"

"You worry. And it's sweet that you worry. But I'm not used to having people worry about me, and until I adjust to that, you need to give me some breathing room," Meredith said carefully, hoping she wouldn't upset Derek or his ego.

He nodded, looking slightly defeated.

"Derek," she started, locking her eyes with his. "I like that you care so much. I do. Just, talk from now on. Talk to me. I'm not so fragile that you need to protect me from everything. And I'm really trying to work on this communication thing between us," she confided. She leaned down and kissed him gently, somehow emphasizing her point.

"Okay," he whispered as he pulled his lips away from hers. He pulled her sideways into his lap and wrapped his arms around her, cradling her close. Her legs dangled over the arm of his chair and her head rested against his shoulder.

"Are you going home tonight?" Meredith asked quietly. She closed her eyes and listened to his heart's rhythmic beating. Thump. Thump. Thump. She could let this lull her to sleep so easily. She'd already been working for thirteen hours of her thirty-six hour shift, and her day had been emotionally exhausting.

"No, I'm going to stay. I'm getting a lot done, and I have surgery early tomorrow," Derek softly responded. He raised his hand and started running his fingers through her hair, inhaling the faint lavender scent that lifted from her honey-colored strands.

"You know I won't be done until ten tomorrow night," she sighed, barely clinging to consciousness.

"I know, I'll be here." He kissed her forehead tenderly, and tilted his head against hers.

Her breathing became slower and deeper, marking her descent into sleep. Derek was happy to let her doze in his arms for a while, even if it was a little uncomfortable. She didn't snore, but she occasionally murmured softly, causing him to open his eyes and smile before drifting back to sleep himself.

"Shit! Make it stop," Meredith groaned after several minutes. She reached down and pulled off her pager, eyeing it angrily for interrupting her sleep.

Derek woke up suddenly and nearly knocked Meredith off his lap in the process. His arm and legs were asleep, and pins and needles danced through them as he tried to regain circulation.

"You have to go?" he asked, a little disappointed.

"Yeah," Meredith replied, standing up quickly.

He was always amazed at how easily she could wake up when she was on call. At home, waking up tended to be more of a battle for her.

"Text me later and tell me where you decide to sleep. I'll come to your room when I get a chance," Meredith smiled, rubbing the final remnants of sleep from her eyes.

"Sounds good," Derek replied. Even though they still had a lot to work out from the day's events, he felt satisfied. They were making progress, and despite the arguments, they were still together at the end of the day.

Meredith ran out the door to respond to her page, and Derek went back to work at his computer.