AN:

According to the CSI Companion, CBS site, the show and I have worked out the following. Some are approximates because we tend to get differing ideas. All of which are important for the story:
Gil Grissom was born on 17th August 1956. Gil was in LA when he was 22.
Catherine Willows (nee Flynn) was born on 26th March 1963. Her father is Sam Braun, her mother was a showgirl.
Catherine started dating Eddie in 1986. She's hooked on coke at the time and enters a rehab center at Gil's urging.
Catherine started night school in 1983 and graduated school May 1987.
She gets a job at the university lab in May, before she starts working at the Las Vegas Crime Lab in September 1987.
Lindsey was born in 1993. Catherine married Eddie when she was two months pregnant. She was CSI-2 at this time.

Thanks to SJ, Thais and Lisa for helping me out :)

July 15th 1969 – Las Vegas

Standin' on a mama's porch
You told me it would last forever
Oh the way you held my hand
I knew that it was now or never
Those were the best days of my life

He was almost fourteen years old. Exactly one month and 2 days left of being thirteen years old.

He was lucky that his mother hadn't sent him on summer camp this year. He'd claimed that at almost fourteen years old, he was too old for summer camp.

Instead, he'd requested a vacation in Las Vegas, so he could poke around the number one forensics lab in the country.

His mother had been surprised, and slightly concerned, until she'd agreed to let him go, as long as she could come too.

Gil Grissom didn't think his mother liked Las Vegas much.

Frankly, if it weren't for the forensic and entomological richness of the city, he wouldn't like it either.

He found himself wandering down the Strip. All he wanted was a really good burger. Preferably with a pickle.

His hands in his pockets, he jingled his guest badges for both the Las Vegas Crime Lab and the University of Las Vegas.

As an observer of the human race, Gil looked into the open doors of all the places he passed. Someone hit a jackpot in one casino. Two men argued over a half-naked woman in another.

Gil paused. His mother would certainly not approve.

Moving to the next casino, Gil was almost bowled over by a little girl.

He grabbed her hand before she ran out onto the street. "Are you insane? You'll get killed!"

The small strawberry blonde looked up at him, a mischievous smile on her face. "Haven't yet."

"How old are you?"

The little girl's eyes narrowed. "How old are YOU?"

Gil found himself vaguely irritated by this child. While her blue eyes were full of mischief, and her smile was teasing, one hand had been firmly planted on her hip and one of her feet was tapping on the ground in the glossy black Mary Jane.

"I asked first," Gil said.

"I'm six. And I'm very busy, so you're just going to have to let me go…" She tried tugging her hand out of his.

"I think we better find your parents."

The little girl continued the attempt to yank her hand out of his. "Yeah, well good luck with that. Who do you think I'm looking for?"

"You've got a lot of attitude for a six year old." Gil cocked his head. "Do you live here?"

She gestured to the Tangiers. "My uncle Sam owns it. And if you don't let me go in five seconds, I'm gonna scream." She fixed her eyes on his. "And believe me, I can scream."

"I don't doubt it," Gil replied. "But I'm not letting you run around Las Vegas by yourself. It's not safe."

"And being held onto by a stranger is?" She opened her mouth, ready to scream.

"CATHERINE FLYNN! What do you THINK you are doing?"

The little girl's eyes widened and she tried to tug her hand out of Gil's as a woman emerged.

When Gil caught sight of the woman – a sequined leotard, feathers everywhere and bright red hair – his eyes widened too.

He quickly swallowed his nervousness and adjusted his glasses with his free hand. "Uh, ma'am? Is this your daughter?"

Lily Flynn took Catherine's other hand and tugged her close. "And who do you think you are? You better start explaining before I go inside and start dialing the cops."

"Mother," came the bored tone of the girl.

"I'm Gil Grissom," Gil replied. "Catherine was trying to run across the road. I just didn't want her to get hurt."

Lily paused and looked down at her menace of a child. "Well, thank you. I appreciate it." She leant against a pole. "And what are you doing down here all by your lonesome?"

Gil gulped.

"MOTHER!" Catherine growled.

"I…uh, erm…I'm visiting Las Vegas," Gil said. "And I better go. I'm going to be late."

"Thank you for taking care of her," Lily said, going back inside, taking Catherine with her.

Of course, Catherine being Catherine, she snuck back out again.

Gil was about to continue on his way when he felt a vicious poke in his back. Startled, he whipped around, ready to bolt, when he found Catherine's impish face staring back at him.

"What did you poke me for?"

She grinned. "You still didn't tell me how old you are. I told you, so it's only fair if you tell me back."

Gil rolled his eyes. "I'm almost fourteen."

On hearing how old he was, Catherine's eyes nearly bugged out of her head. "Geez! You're ancient!"

With that parting shot, Gil watched in amazement as the blur of energy raced back into the Tangiers.

--

Song used - "Summer of '69" - Bryan Adams