Aiden rose early in the morning as had become her custom the last few weeks, showering and grabbing a cup of coffee before Don's alarm even went off. She had been arriving at work hours before her scheduled start time, always with the story that Don snored so loudly that if she woke up early she couldn't get back to sleep. She consistently delivered her lines with a wink and a smile and people were polite enough to leave it at that, but the smile was always a bit forced and no one believed the explanation.

She peeked in the doorway of the bedroom one more time before leaving, watching her boyfriend sleeping peacefully in their bed. She wondered for the millionth time how she was ever going to tell him, if she was going to break his heart, and concluded that she probably would, but knew she had no choice. She frowned and shook herself, heading out the door and off to work.

When she arrived at the lab she caught sight of Danny pulling his lab coat off and exchanging it for his suit jacket.

"Where are you goin'?" she asked.

He smiled broadly. "B & E in the Bronx."

"First day back in the field," Aiden remembered. "You ready for this?"

"I'm more than ready for this. I've been itchin' to get outta the lab for weeks," he reminded her.

She smiled a little. "I know. Just be careful out there, okay?"

"I will," he promised.

She squeezed his shoulder affectionately as he turned and left with a bounce in his step. She watched him disappear through the door, thinking of the last breaking and entering case he had worked. It had been unofficial, of course, but she couldn't get the image out of her mind of Danny lying on the floor of the jewelry store, his life bleeding away from the bullet hole in his shoulder.

She shook herself for the second time that day and tried to banish the thought from her head, but knew it would only be a matter of time before it returned. It always did.

Stella found her a few hours later in the break room.

"Hey Aiden, have you seen Danny?"

"He's out in the Bronx on a B & E," Aiden responded.

Stella frowned. "I tried calling him on his cell but he isn't answering…"

Aiden tried to keep from panicking, knowing it was an overreaction. "Let me try…" She flipped open her phone and dialed the number from memory, hearing ring after ring in her ear before his voicemail picked up. She looked at Stella and shook her head.

"Well, I'll keep trying. He's bound to turn up sometime."

Aiden nodded, but felt the fear invading her consciousness. She knew it was irrational, but so had a lot of her feelings been over the last few weeks. She tried to go back to work, but continued to call Danny's cell every half hour, becoming more and more anxious with each message left. Emotions from his shooting flooded back as she remembered the torment of waiting for him to come out of surgery, wondering if she was losing her friend forever.

She put her head down on the counter, burying her face in her arms as she sat alone in a corner room of the lab. She remembered how scared she had been for Danny, how she hadn't stopped being afraid even after he was released from the hospital, how everyone else seemed to be able to move on. She thought about all the nights she hadn't slept, worried that it would happen again, that she would lose Danny, or Mac or Stella…or Don.

Tears began to roll down her cheeks as she remembered the day she had made her decision. She had been out on a call several weeks after Danny's shooting when a car had backfired. By sheer coincidence, a fly buzzed past her ear at the same moment and she had frozen in terror, sure that someone had taken a shot at her and unable to move to escape any subsequent shots. She had turned in her resignation to Mac that very afternoon, promising to stay until Danny was back to full duty, but making him swear not to tell another soul about it. She wanted to just slip away when the time came, out of their lives as though she was never there, to leave them before they could leave her.

She cried quietly for a few more minutes before picking her head up off the counter, realizing she was still in a building full of people. She made a quick trip to the bathroom to splash some water on her face and pull herself together, then ventured back into her secluded little room to finish writing her final report for her last case.

By the end of the day everything was in order, the last t crossed and the last i dotted. She pulled off her lab coat, running into the locker room to grab her things on the way out. Before she left, though, she decided to stop by Mac's office, where she found him sitting at his desk squinting over his own paperwork.

"Some day you're gonna go blind," she teased gently, entering the office and sitting down across from him.

He looked up and smiled. "I don't doubt it."

There was an awkward silence between them, both knowing why she was there, but neither wanting to talk about it.

Finally, Mac spoke again. "You finished up the report on the Thomas case?"

She nodded. "Yep. Signed, sealed, and delivered to the DA."

They were quiet again for a moment before Mac pressed his lips together. "Aiden, are you sure you want to do this?"

She smiled sadly. "Yeah, Mac, I'm sure."

He nodded, frowning. "You're positive?"

"I don't like it either, but this is something I have to do."

He looked her in they eye, seeing the pain there, the exhaustion, and knew she was right. "All right. But if you ever want to come back, there's a place here for you."

They rose from their chairs and walked toward the office door together.

"Thanks," she said in a low voice, trying to keep her emotions in check. Impulsively, she slid her arms around his neck and hugged him tightly. "Thank you for everything."

He hugged her back, both surprised at and expecting her gesture. "You stay in touch, you here?"

She released him and nodded, trying to hold back her tears. "I will. And you'll explain things to everyone?"

"I'll take care of it." He paused, squeezing her shoulder. "They'll understand, Aiden. They're your friends, and they want what's best for you."

She smiled. "They do." She hugged him again, quickly this time, and hurried out of the office.

Aiden took a deep breath as she climbed into her car and managed to drive herself home, where she gathered her things and called a taxi. Part of her wanted to wait for Don to come home, but he had left her a message that he'd be working later than planned on a new case he'd been given. Not knowing what else to do, she scrounged around the apartment until she found a blank piece of paper and a pen, then sat down to write the most agonizing letter of her life.

Dear Don,

You may not understand why I'm doing this now, when things are going so well between us, but please know that I'm only doing it because I have to. I love you so much…

By the end of the letter the tears she had shed earlier were back, spilling from her eyes in such numbers that she could hardly see. The taxi arrived in front of the building and blew its horn, and just like that it was time. She folded the letter carefully and printed Don's name on the back, leaving it on the kitchen counter and grabbing her suitcases.

The cabbie helped her with the bags when she arrived downstairs, and she climbed into the back of the car.

"Where to, miss?"

"Penn Station," she replied in a shaky voice.

Halfway to the train station she tapped on the cabbie's shoulder. "I need to make a stop first," she told him, giving him Maddie's address.

They pulled up in front of the building and Aiden hopped out. "If I'm not back in ten minutes, honk the horn," she managed to say. The tears started up again before she even reached the front door, and she could barely get out her name when Maddie answered the buzzer.

Maddie met her at the elevator door. "Aiden! What's wrong?" she asked, pulling her friend toward her in a consoling hug.

"I thought I could do it," Aiden sobbed. "I thought I could leave without saying good-bye, but I can't…"

"Leave? Aiden, where are you going?"

Aiden took a deep breath and pulled back. "I'm leaving the lab, I'm leaving the city, I'm leaving the east coast…" She broke down again, burying her face in Maddie's shoulder, weeping as though her heart was breaking. "I have to go," she continued after a few minutes. "This job is killing me, and I'm dragging down everyone I love with me…"

The anguish in her voice pierced Maddie's heart and she felt tears welling up in her own eyes.

"I wanted to just disappear," Aiden continued. "I thought it was best that way, ya know? But I feel like such a coward…leaving the best friends I ever had…leaving Don…" Her voice caught in her throat as she spoke his name. "He's the One, Maddie. I'm more sure of that than I have ever been of anything else in my life, but I'll destroy him if I stay…and all I could do was leave him a note…I'm such a coward…"

"You are a lot of things, Aiden Burn, but you are not a coward," Maddie told her firmly. "If you feel like you have to leave to save yourself, then that's what you need to do."

Brown eyes met blue ones as Maddie spoke, and Aiden felt a small measure of comfort in her words. The taxi blew it's horn and Aiden looked at her watch.

"I have to go…my train is leaving soon…" She hugged Maddie tightly one more time, sniffling as she tried to calm herself for the ride to the station.

"Promise me you'll keep in touch," Maddie instructed, pushing the elevator button for her friend. "Wherever you go and whatever you do, promise me you won't disappear completely…"

Aiden tried to smile. "I promise," she said softly, wondering if she meant it.

"And if there's anything you need, ever…"

Aiden nodded. "Thanks." The elevator car arrived, and she turned and quickly fled, leaving Maddie standing alone in the hallway.