A/N: Hi everyone! Addison and Derek aren't the couple that I usually write about, but I seem to be developing a soft spot for them. This story is set towards the end of the seventh season of Grey's Anatomy and the end of the fourth season of Private Practice. I hope you enjoy it, and I'd love to hear what you think! Thanks so much for reading! :)

After All

"Are you ready for this, Mer?" Derek asked excitedly, as he and Meredith stood in City Hall, prepared to legalize their post-it marriage.

"I am," Meredith smiled. "It's about time we made things official."

"Drs. Derek Shepherd and Meredith Grey," a woman, whose nametag read 'Lucy,' called out from behind a desk. "We're ready for you."

"This is it," Derek smiled, squeezing Meredith's hand, as they made their way up to Lucy's desk.

"Okay," Lucy said, "I just need to see your paperwork to make sure that everything checks out before I send you over to the judge."

Derek and Meredith nodded, handing Lucy the necessary information.

"Okay, everything looks good, Dr. Grey," Lucy said, as her eyes scanned over Meredith's paperwork. "Now, let's see, Dr. Shepherd…okay, everything looks…oh, wait a minute," Lucy interrupted herself, her eyes widening in disbelief. "I'm sorry, Dr. Shepherd," she apologized, "but I cannot authorize your marriage today."

"What?" Derek asked in surprise. "Why not? My paperwork is perfect. Why can't we get married today?"

Lucy looked at him in amusement. "I'm sorry," she apologized again, "but the reason you two can't get married today, Mr. Shepherd, is-"

"Dr. Shepherd," Derek interrupted. "It's Dr. Shepherd."

"Dr. Shepherd," Lucy amended. "The reason you and Dr. Grey can't get married today is because, well, you're already married."

"I'm what?" Derek gasped, gripping onto the side of Lucy's desk to stop himself from collapsing.

"You're what?" Meredith shrieked. "This is like a bad case of déjà vu. Derek Shepherd, you have some serious explaining to do"

Derek turned his attention to Meredith, and then back to Lucy. "I'm sorry," he said, loosening his grip on her desk, "but I must have just misheard you…because if you just said what I think you just said, well then-"

"You're already married," Lucy repeated slowly, as Derek felt a fresh wave of dizziness wash over him.

"Married?" he choked out.

"Who the hell are you married to, Derek?" Meredith demanded angrily.

"I have no idea," Derek admitted, still feeling light headed. "I came here with the intention of marrying you. There's clearly some kind of mistake; some kind of identity theft or something."

"Oh, no, there's no mistake," Lucy insisted. "You, Derek Christopher Shepherd are still very much married."

"To who?" Derek demanded, angrily jamming his hands on his hips.

"Now, Dr. Shepherd," Lucy rebuked, "I don't appreciate you using that tone of voice with me. After all, I'm just doing my job."

"Right, fine, I'm sorry," Derek apologized.

"He really is," Meredith added. "This is all just very, um, uh…unexpected. So, Lucy, can you please tell us who Derek is married to so that we can fix this?

Lucy nodded. "Well, it says right here that you, Dr. Derek Christopher Shepherd, are still married to Dr. Addison Forbes Montgomery-Shepherd."

"Addison?" Derek and Meredith exclaimed together.

"Oh, good, you know her," Lucy said.

"She's my ex-wife," Derek told her.

"Well, not according to these papers," Lucy chuckled.

"But we got divorced nearly four years ago," Derek insisted.

"It looks like you tried to get divorced," Lucy explained, "but look," she said, showing Derek the divorce papers. "You and Dr. Montgomery-Shepherd signed on the wrong lines; you signed where she should have signed, and she signed where you should have signed. This makes your divorce null and void. You two are still married."

"You have got to be kidding me!" Meredith exclaimed. "Addison Montgomery has a special talent for making my life miserable."

"Her legal name is actually Addison Montgomery-Shepherd," Lucy reminded Meredith with a grin.

"Right, whatever," Meredith muttered. Then turning her attention to Derek, she asked in annoyance, "You mean to tell me that the whole time that we've been dating, you've still been married to Addison? Hell, we had a post-it marriage while you were still married! How could you do this to me, Derek – again?"

"Look, Mer, I had no idea that Addison and I were still married. I'm sure there's an easy way to fix this." Derek turned his attention to Lucy. "Please tell me there's any easy way to fix this," he begged.

Lucy nodded. "It's pretty simple," she told Derek. "You and your wife-"

"Ex-wife," Derek interrupted.

"Not according to these," Lucy said smugly, gesturing towards Derek's divorce papers. "Anyway, do you want my help or not?"

"Sorry, go on, Lucy."

Lucy smiled. "You and your wife need to meet with your lawyers and correctly fill out your divorce contract."

"And then we're good?" Derek asked.

"Then you're good," Lucy grinned.

"You hear that, Mer?" Derek asked. "We're good."

"Oh we are not good, Derek," Meredith responded angrily. "We are anything but good."

xxxxx

Twenty-four hours later, Derek was standing at the front door of Addison's beach house. Meredith refused to have anything to do with him until he got divorced from Addison – for real. He had no idea how to tell Addison what he was about to tell her, but he figured that he at least owed it to her to break the news in person. He had no idea how Addison was going to react when he told her that they were still married – she'd probably be angry and upset and surprised – so he promised himself that he'd break the news to her as gently as he could. He took a deep breath, straightened his shoulders, and rang the doorbell.

"Derek," Addison said in surprise. "What are you doing here?"

"Um, well, the thing is, um, we need to talk, Addison."

Addison nodded. "Okay, but can we maybe talk later? Now's actually not a good time."

"Trust me, Addison; there will never be a good time to have the conversation that we're about to have, so I just need to rip the Band-Aid off now. Your living room's this way, right?" he asked, as began making his way through her house.

"Yeah, but Derek, can't we just talk right here?"

"We need somewhere with a couch," Derek insisted, as he entered the living room. But, to his surprise, the couch was already occupied. Sam Bennett was lounging on Addison's couch, as if he owned the place.

"Derek," Sam grinned, rising from the couch. "It's good to see you."

Derek had no idea why, but he felt a wave of anger and jealousy wash over him and, suddenly, his plans of gently breaking the news to Addison went out the window.

"So," Derek smirked, reaching out to shake Sam's extended hand, "you must be the man who's been sleeping with my wife."