A/N: I'm back! My trip to Manhattan was fantastic...I'm exhausted now, after so much walking in such cold weather, but what a good time! I will admit, though that I thought of Mac when we visited Ground Zero (and the real-life people who went through what he went through)...and that every time we got on the subway I peeked out the window to see if there was anything on the tracks ;)

Anyway, here's the next in the line of firsts for Mac and Stella, with at least a few more still to come. Enjoy!

He had been looking at her funny all day.

Stella was working with Mac on a case and noticed how several times that day he had looked over at her as though there was something he wanted to say to her. Once or twice he even opened his mouth to say whatever it was that was on his mind, but then thought better of it and closed it again.

It must be something personal, Stella thought. The two of them had agreed that while on duty, in the confines of the lab or at a crime scene, they would treat each other strictly as colleagues and friends. Anything romantic or otherwise out of the ordinary would have to wait for a more appropriate time and place in order to maintain the integrity of the lab. Which means I'll have to wait until after work to figure out what's going on in that brain of his.

She pressed her lips together and glanced at him out of the corner of her eye. He was focused on pulling a bullet out of a wall as carefully as possible, gently coaxing it from the plaster with an expression of pure concentration that Stella always found so sexy. She shook her head a little and allowed a small smile to form on her lips before turning back to the blood smear she had been inspecting. Waiting was not going to be easy today.

When end of their shift finally did arrive, Stella's curiosity was bursting at the seams. She discreetly waited for him in the locker room, slowly pulling her hair from its pony tail and running her fingers through it before tugging on her jacket.

Just as she was about to walk out the door, Mac walked in. "Perfect timing," he smiled.

She nodded. "Yeah, you can walk me to the subway station."

"Why don't you let me drive you home?" he asked, opening his locker and removing his overcoat.

This time she shook her head. "My apartment is out of your way, and you need to go home and get some sleep. Besides, I don't have the patience to deal with traffic at the moment."

"Okay," he chuckled. "When you put it that way…"

They headed out into the chilly winter air, clasping hands almost as soon as they were clear of the building, walking along in comfortable silence. When they reached Stella's subway station, though, the pair paused, smiling shyly into each other's eyes as they began their good-byes.

"You're sure you won't let me drive you home?" Mac asked, turning toward her and taking her free hand in his.

Stella took a step closer to him and grinned. "No," she repeated. "'Cause I'll invite you in, and you'll say yes, and we'll stay up entirely too late keeping each other company."

His eyes twinkled as he replied, "Is that so terrible?"

"No," she laughed. "But you really do need to get some sleep, Mac. Between work and me, you're not getting enough rest and I won't have that."

The smile on his lips grew. "Okay boss. I promise I'll go home and go straight to bed."

They shared another laugh and Stella leaned forward, her mouth finding his in a soft kiss. She was still smiling when she pulled back, but the expression from earlier in the day returned to his face and she knew there was something on his mind.

"What is it?" she asked quietly.

He smiled a little in spite of his racing thoughts. She always knew what was going on with him, even when he didn't say a word. But just as quickly as it came, the smile left and was replaced by a more grim look. "I…I don't…know how to say this," he began hesitantly.

She squeezed his hands reassuringly. "It's okay," she told him. "Whatever it is you can tell me."

He looked into her sparkling eyes and spoke what was in his heart. "I love you Stella."

Her pulse raced at his words and a broad grin crept across her face, but Mac maintained a sad, frowning expression. She took another step closer to him and tried to tone down both her smile and her puzzlement. "Is that so terrible?" she asked, repeating his own question with a half-hearted wink.

"Of course not," he replied, letting out a breath. "I'm so happy I can't even describe it…"

He was sincere about that, she could tell. He really was absolutely ecstatic to be in love with her, but there was something that was holding him back. Rather than probe for details as she so often did on the job, she instead allowed him to collect his thoughts and continue.

After a moment, he did speak again, squeezing her hands both as a sign of affection and to help him verbalize his feelings. "I love you so much, Stella…but…Claire…" He looked down at the sidewalk, unable to meet her gaze any longer.

Her arms slid around him, pulling him to her in a warm embrace. "I know," she whispered in his ear. "I know how much you loved her…how much you still love her… You'll never forget her, Mac, and I wouldn't want you to. I love you for who you are, and Claire's a part of that." She paused, rubbing a hand over his shoulders and kissing his cheek. "I want you to know," she continued softly, "that I'm not trying to replace her."

He pulled away quickly and looked into her eyes. "Oh, Stella, no…I know you aren't…"

She touched his face tenderly and smiled. "I love you," she told him a second time, "and I'll do anything to be with you. Even if it means we need to slow down, or take a break…whatever you need…"

Mac pulled her close again and rested his forehead against hers. "We're going slow enough," he decided, "and I definitely don'twant to take a break. I just need to deal with this myself. But if I'm acting distant or inattentive it isn't because my feelings for you have changed…just be patient with me." He stopped for a moment, letting his lips break into a smile and adding, "…more patient with me than you are with traffic."

"If it was anyone else, Mac, I'd say no," Stella laughed. "But for you I'll give it a shot."

He grinned and kissed her lightly. "Thanks."