Catherine felt like an intruder.

There she stood, pacing, on Grissom's doorstep, two hours after her last shift.

It was the end of a triple shift for Grissom. And the man had the flu. The first time he's been sick in… she'd have to check records to see when the last time it was he took a sick day.

At times it seemed as if the guy never left the building – every time she turned around he was on a new case or doing endless amounts of paperwork.

Gil Grissom hated paperwork more than anything, yet he remained glued to his office chair for hours on end, filing through the endless piles, and going home only when mentally and physically exhausted.

She knew why. Sara.

The entire team had tried reaching out to him – Nick offered to take him to breakfast, Warrick had mentioned the team being different without her, Catherine had told him "to go after her", hell even Hodges had reached out to him.

Yet he remained the same stubborn, cold hearted Grissom.

She saw the toll Sara's leaving had taken on him in the past few months. His blue eyes no longer held the spark they did while working cases; at times it seemed they had gone gray. His hair was just a little bit grayer, the beard had returned, and the dark circles below his eyes all spoke of his boxed up sadness.

But she had also seen the complete opposite of the current Gil Grissom. She saw the look of love and sheer terror in Grissom's eyes when he confessed to being in love with Sara almost a year ago. She had never seen the man so determined when Sara was the one taken by the miniature killer. When they found her, the look of terror returned, but also relief because they had, in fact, found her.

The level of their love and trust was exposed – just a little – when Sara came out of surgery at the hospital. Everyone was worried about her, but not like Grissom was. Surgery took around three hours to reconstruct the bone in her left arm. Gil Grissom paced in the waiting room for the entire three hours, quietly reciting baseball stats for a little while, and then switching rattling off scientific names of insects, while waiting for the doctor to come and tell everyone that she was going to be okay. When he stood at her side, waiting for her eyes to open, she could almost hear his silent prayers.

When she looked up at him, and he down at her, the unhidden love and happiness written across Grissom's face left no doubt how deep his feelings went. His eyes went sky blue and filled with tears. A small, soft smile went across his face, his features slackening, making him look ten years younger. As he leaned down to kiss her, the tension left his shoulders, and it looked as if he could've fell to his knees.

The team left them alone, only for Catherine to return around 30 minutes later, Grissom sitting in a chair next to the hospital bed, hunched over to Sara's body, Grissom's hands surrounding her one free hand, both sound asleep, Gil for the first time since he had found out Sara had been taken.

Now, just over 5 months later, all of Grissom's happiness of Sara being home and healthy was gone.

Because Sara was gone.

But Catherine was nosy. She was persistent. She had sympathy for the man, but at the same time wanted to know one thing; why.

Why did Sara just get up and leave? Leave the lab, her job, Grissom, and everyone in the lab wondering what is going on?

All the questions in Catherine's mind is what stopped her pacing outside Grissom's townhouse and knock on the door.

She heard a dog bark from the other side, Grissom mutter something, and then his footsteps walking to the door.

"Catherine?"

"Hi, Gil, uh…can I, can I come in?"

Sigh, "Sure." Stepping aside, a robe and slipper-clad Grissom let her walk past. He looked terrible. His hair was more unruly than usual; the darker than usual circles below his eyes indicated virtually no sleep in the past several days. Change that. He looked like hell.

Stepping just inside, a 90 pound growling boxer stopped her in her tracks.

"Uh, Gil?"

"Yes?"

"Gil?!"

"Oh, Catherine, this is Hank. Hank, Catherine," tilting his head, Hank questioned his master, as Gil continued, "Be nice, it's okay."

As soon as Grissom said its okay Hank quit growling and started to wag his tail back and forth. Catherine bent down and scratched behind his ears. The small amount of attention sent the dog into a frenzy – he immediately rolled over onto his back and started thumping his left leg around in the air. Tongue hanging out and a contented sigh left the boxer as Catherine started to scratch his chest just a little.

"You do that, he won't let you quit, Cath," said Grissom, who had walked back into his kitchen.

Catherine stood and followed him, smiling just a little at seeing her long time friend, and supervisor, walking through his house in just a blue checkered robe and slippers.

"Ah, Cath, I'll uh, be right back. Help yourself to something to drink if you want."

Taking Gil up on his offer, Catherine walked over to a cupboard where she knew his glasses were kept, and noticed they weren't there anymore. Nor were they in the one to the right, or left.

That's when it dawned on Catherine, this isn't just his home anymore… it's theirs. Taking a small glance around, the changes in his home became very apparent. It had been several years since the last time Catherine had been at his house, and she didn't know how long the two of them had been together, but it had to be a while. The leather clad piece of concrete Gil liked to call a couch was no longer there, but a plusher, navy blue couch was in its place. The tile that once went across his entire floor now only extended into the kitchen, now an earthy brown carpet covered his living room. Of course, various creepy-crawlies had been put up around the walls and in frames, but other items of non-insect décor had taken place around his house. And… she could tell two book nerds lived here, as one entire wall was completely plastered with books.

Turning back to her task of finding a glass, she finally found the cupboard containing the glasses, took a small one off the shelf, and went to his refrigerator.

Several different choices stared back at her, after a moment of thought she settled on a glass of orange juice. Setting the glass on the counter, she put the orange juice container back into the fridge and shut the stainless steel door, blindly staring for a minute. Several different things covered the door – notes, takeout menus, phone numbers, and… a picture. Of them.

Pulling the picture free of the magnet, Catherine took a better look at the picture, and noticed how… happy they looked. Sara was pulled into Grissom's side by his right arm, smiling brightly. Gil had a content and typical smirk across his face. The look of just… happiness between the two of her almost took Catherine down by the knees. Sara didn't look to be 25, and Grissom looked so handsomely young as well.

Turning to her left, she saw Grissom staring at her, now in jeans and a t-shirt.

"Gil, when uh, when was this, this picture taken?"

Looking down at the picture in her hand, he stared at it and spoke, "Almost ten years ago. In San Francisco."

"Is uh, is that when you two met?"

"Yea sort of."

"Sort of?"

Letting out a frustrated sigh while running his hands through his hair, "Catherine, if you don't mind me asking, why are you here? I'm exhausted; I'd like to try to sleep a few hours, even though I know that won't happen..."

Hearing Gil brush her off, the persistence in Catherin Willows set in. She wasn't going to let her questions go unanswered. Interrupting his spew, "Gil, I'd like to know what happened between you two…not every little detail, but…"

"You want to know why."

Nodding, she quietly answered, "Yes…"

The frustration in his eyes apparent, Gil knew Catherine had her mind set in getting something out of him. And quite frankly, he was too tired to care.

"Cath, there are things about Sara that I won't speak of. She had a…rough… childhood. She was a foster child after age eight until she graduated high school early at 17. Prior to that I will not speak of. She had a hard time growing up, she never fully… let go of her past. And she needed to…clear up some… things."

Gil's stuttering left much to be desired on Catherine's part.

"I really can't talk about this now, Catherine. Maybe some other time…" as Gil stood to usher her out the door, her temper flared.

"Gilbert Grissom! You are NOT kicking me out without answering some of my questions!"

Stopping mid-track, Grissom knew she was in her mood where "no" was not an answer.

Sitting back down, Gil just…sat there.

"Gil, I'm sorry for blowing up, but dammit… you just can't keep walking around like a zombie pretending everything is okay, because obviously it's NOT okay. Look… you don't have to tell me everything. It's just...we don't know anything about why Sara left. All we know is what you let us. And quite frankly, it's nothing. You won't let us in on anyth-"

"Catherine stop, please. Okay. I'll…tell you a little. You ask. I'll answer. But don't ask about Sara's childhood, I won't tell you that."

"Can you tell me about the picture?"

"Excuse me?"

"Tell me about the picture of the two of you on the refrigerator."

Standing up to get it, she could see Grissom struggling if he wanted to go down that road with Catherine or not.

It was such a happy time in Gil's life. Sara had plagued him with more questions about anthropology than he thought possible, a few even stumping him. He was not an anthropologist, but no student had ever prodded his mind the way Sara's had. At the end of her question marathon, 45 minutes after the end of the lecture, the two of them ended up sitting in desks across from each other, just talking. Her amazing mind kept his on the edge, but her curly hair, tall, slender figure and that adorable gap between her teeth is what kept him staring at her.

The invitation to a casual dinner completely caught him off guard. She was a San Francisco native, and offered to show him around the city. How could he turn down an offer like that?

In a detached tone, Grissom began, "She asked so many questions. One including a dinner invitation and a San Francisco tour."

"How did you meet her?"

"It was the Forensic Academy Conference. Ten years ago. She was taking an advanced lecture I gave in the evolving science of forensic entomology. I was finishing up the last bit of research on my Ph.D."

Staring at his folded hands, Grissom's answers were short and dry. Almost as if he was trying to keep a passive tone to the memory.

"When was the picture taken?" prodded Catherine

"By the Golden Gate Bridge. There wasn't a cloud in the sky; we just walked along the sidewalk, taking in the sunset and the bridge in the background. After a while her arm was draped through mine. To make a semi-long story short, Sara asked a passerby to take this picture for us. There you have it."

"Were you…dating?"

Running his hands over his hair, she could see that there was almost bitterness to the way he recollected the memory.

Catherine spoke quietly, "Gil… I would think this would be a happy memory. Why are you still so… upset?"

"The memory is happy, Cath. That was the happiest time of my life. The problem is… I had to walk away from her; even though that was the last thing I wanted to do. I had to break her heart."

"Wha- I uh, don't follow…?"

Pointing, Gil gestured at the picture, "Do you know how old she was at the time that picture was taken, Cath?"

Thinking for a minute, Cath replied with "probably around 25, why?"

"I was just shy of turning 40, Cath. I had a job as a CSI here in Vegas. She was a newly promoted CSI II at San Francisco's lab. When she asked about job openings at the lab here in Vegas, I had to put the brakes on. She wanted to follow me. I couldn't let her give up her life for…me."

"What happened?"

"Two days after the conference ended, phone numbers and emails exchanged, I flew home. For almost a month communication was at a zero. Finally I sent her a very short email asking how San Francisco was, how work was and if she was okay. She did write back, and from there we became…friends. I took on a mentor roll and nothing more."

"Gil…when she first came to Vegas, right after Holly's shooting, you were more than a mentor. You've always been more than a mentor to her. Did…something…something else happen at the conference?"

"You mean romantically?"

"Well…yeah."

A sudden smirk crossed Gil's face. Fiddling with his hands, he spoke softly, "Yes, Catherine. But it also depends on what your definition of 'romantic' is."

Putting up a hand, Catherine had to laugh just a little, almost choking on the sip of orange juice she took, as she said, "S'Okay, Gil, I uh, don't need details."

His tone completely different, he began, "We held hands and linked arms while walking the streets of downtown San Francisco. I held her in my arms and watched her sleep for almost three hours one night. I kissed her with more passion than any other woman in my life. We…basically behaved like two teenagers, because neither of us wanted to go any further. One evening, we were at her place watching a movie, she fell asleep partway through. When I looked down at this young, beautiful… innocent woman in my arms, Cupid's arrow snapped. She was 15 years younger than me, just barely starting her career. I was her professor, she my student, hell if you really want to stretch it; technically I'm old enough to be her father. At the time I forced those thoughts to the back of my mind so that I could savor the moment. The next morning I'd have to break her heart and walk away."

Catherine couldn't believe she was getting so much out of Grissom; she thought about stopping him. But instead, she simply decided to let Grissom go on his trip down memory lane.

"It was heaven having her and hell to let her go. I didn't want to wake her, so we both fell asleep on the couch, and we woke up together. After a while we sat with coffee, and she asked about job openings."

Grissom stopped talking and just stared at his tightly clasped hands. After a moment, Catherine finally spoke quietly, "Gil?"

"I made her cry. I hurt her so bad. Yet she still came back to me. She pursued me for almost six years; it took a crazy man holding her at knife point for me to come to my senses."

"Have you two… spoken since she left?"

"Yes. I called her cell phone almost immediately after I read her letter, and got her voicemail. All I told her was that I wanted to know that she was okay. I didn't care where she was going, or how long she would need to be gone, I just wanted to make sure that she was safe, and that she was… that she was okay."

"And?"

"She called me about six hours after I left that message. The conversation lasted less than a minute. All I knew was that she was in San Francisco, going to visit her mother."

"Have you talked since then?"

"We talk maybe around once a week, very short conversations. She now likes to call and leave voicemails on my land line while I'm not here. She usually says more there than the business talk that we've become accustomed to because she's always busy. A few weeks ago I told her I missed hearing her voice. She told me she would do something about it, so that was her trade off. Works for me. When you ask about details… I don't even have details beyond what part of the country she's in."

"Do you think she'll come back?"

"What?"

"Do you think she'll be back…at the lab…?"

"At the lab, no. She's completely burnt out. She kept going and going until she snapped."

"What about you?"

"Huh?"

"Is she coming back to you?"

In that moment, Gil put his walls back up. He folded and unfolded his hands quickly, switching back and forth between the folding and unfolding and rubbing his palms together quickly, the uncertainty in his eyes very obvious.

Standing, she spoke, "Look, Gil, I'll leave after you answer my question. Is she coming back to you?"

"I don't know Cath. I can't make her do anything. I've earned every bit of hurt she's given me, because she put up with double, maybe triple the amount from me. I can only hope she will."

"She loves you, Gil. I've known it for almost as long as you've known her. And I know that you love her."

Walking to the door, Grissom stopped her, "Hey, Cath?"

"Yeah?"

He walked over to her, stopped just a foot away from her, and while looking between her and his feet, he softly spoke, "Thank you. For coming by, and…"

"Gil, it's okay," she touched his shoulder, "Just remember… when one member of your family flies away, you still have us. You're just as much a part of my family as anyone. Remember that."

Nodding, Grissom accepted the hug Catherine gave him. As she began to leave, his cell phone began to ring.

"Who the - " walking back, Sherriff stared him back in the face. Reluctantly answering it, his annoyed tone not hidden, "Grissom."

After a few short answers from Grissom and whoever called him, Catherine questioned who in their right mind would ask Gil Grissom to come into work when the entire team had witnessed him lose his lunch a few hours earlier.

"I'll be there, Sherriff, just… give me 30?" Hanging up, Gil spoke very agitatedly to Catherine, "Was the Sherriff. He needs me to testify in court in two hours." Leaning over the table, he threw his cell phone back to the table, and hunched over, his shoulders quivering from frustration.

"What?! Gil, why on God's earth did you even agree to that?"

"I had no choice Cath, the Sherriff needs me on this one. I have to shower & change, even worse, into court attire. See you back at the lab later."

Walking briskly away, Grissom shut the door to his bedroom, a moment later the shower clicked on. Catherine reluctantly left, knowing what a hellish day awaited a flu-ridden Grissom.