It’s one of TV’s great rags-to-riches stories: Young guy from Las Vegas delivers a global smash hit with his first-ever TV script.

Anthony Zuiker, 47, was not so far removed from his job driving a tram for a Sin City hotel when he managed to field the pilot for “CSI: Crime Scene Investigation” for Jerry Bruckheimer TV and CBS in 2000. A well-arranged marriage of Zuiker with veteran showrunners Carol Mendelsohn and Ann Donahue set “CSI” off on a journey that would change the course of TV history and spawn three spinoffs, most recently the Patricia Arquette starrer “CSI: Cyber.”

With the mothership wrapping its 15-year run with a two-hour movie airing Sunday night, creator/exec producer Zuiker spoke with Variety about the emotional experience of writing the finale, reuniting with original “CSI” stars William Petersen and Marg Helgenberger and his deep appreciation for Mendelsohn, Donahue, CBS’ Nina Tassler, Leslie Moonves and others who helped him along the way. And he explained why he still giggles at the sight of a certain high-end department store in Beverly Hills.

Your first TV progeny is about to call it a wrap. How do you feel?

Everybody keeps asking me, ‘Are you OK?’ I’m fantastic. I had the privilege of watching the playback on Thursday with my parents attending. There’s a lot of laughs and a lot of tears story-wise. It felt really good to get a pat on the back from my dad … I have emotionally come to grips with the fact that TV shows have to go up and TV shows have to go down at some point. I would rather have the exit we have. I’m very respectful of the gift that Mr. Moonves gave us — the ability to have closure for our audience. Very few shows have that opportunity.

What was it like to have Petersen and Helgenberg back on the case as Grissom and Willows?

To come back with Billy and Marg and the same team and the same routine is such an incredible joy. When you’re doing an episode you’re usually stressed out about the next script coming down the line. This time everybody came in with the best behavior and we were all committed to the draft. It was a great moment to have where you know you’re seeing something extraordinary (with) top-level people who respect each other to the end.

Was it hard to write the finale as a two-hour rather than the procedural hour-long format?

I’ve never written two 47-page scripts before — they were probably 10 minutes over on both hours. We were able to let the actors come in and do what they do best. It reminded us how you can’t really hire anybody who can do what William Petersen does. You don’t really appreciate until he comes back just how natural it is for him to share the screen with evidence. In one scene he was looking at a bunch of bomb parts on the table and in his imagination (added later with vfx) he sees the parts lifting off the table and coming together as a bomb. When he was acting that out we were so mesmerized by his reaction to watching it being built that the director kept forgetting to yell cut. You forget how good Billy is. He’s just remarkable.

Without giving too much away what is the most important bit of closure that you’ll offer your die-hard fans?

This is the Super Bowl for (Jorja Fox’s) Sara Sidle. She’s applied for the directorship of running the lab. This (case) is the one incident that brings back Grissom, and we see her being mentored by (Ted Danson’s) D.B. Russell. This is a case that paralyzes Vegas. One of the big burning questions of the finale is where (Grissom’s) heart will lie. GSR usually stands for gunshot residue but in this episode it stands for Grissom-Sara Relationship.

Did you have any idea at the beginning that the show would be able to reinvent itself with new cast members?

The short answer is no. ‘CSI’ being my first TV script the last thing on my mind was ‘Is this a format that can last for 16 years.’ I was new to television and new to the industry. But me being from Las Vegas and being a risk-taker, the one thing I wanted to do was come in to TV and break every rule I possibly could. I was a no-name person from Las Vegas who had been driving a tram for $8 an hour. I had to break every rule. We did flashbacks and recreations and “Rashomon” storytelling. In breaking all the rules we constructed this format that crystallized the procedure. You could afford to do anything as long as you had great writing and great mysteries. You could get great actors and continue the journey.

Has technology changed the way you produce the show in the past 15 years?

We don’t make up gizmos or gadgets. If it’s used in the CSI world we can use it but we don’t make them up. What’s been happening (since the show premiered) is more inventions and more improvements of these forensic tools for law enforcement.

How did you tackle the story once you got the word about the movie? You are the sole writer on the finale.

Right after the announcement (of the finale movie) at the upfronts we threw ourselves into a room at Bruckheimer’s office and we broke this thing in a couple of weeks. I went off to write. Louis Milito, a producer for a long time, directed. … As much as I’ve learned from my TV partners Carol and Ann I was happy to write a solo. I was happy to begin as a solo and to end as a solo. It really gave me the chance to prove to them that the kid from Las Vegas who never wrote a script before, after learning from all of their expertise, was about to bring it home. It was a really big thing for me. It was important to me to deliver on a high level for Nina and Les and to my partners (Mendelsohn and Donahue). That’s why I’m not depressed about the end. For me it was the greatest accomplishment.

Does it feel strange to have “CSI: Cyber” on the air this season but not the mothership? The original outlasted the first two spinoffs, “CSI: Miami” and “CSI: New York.”

It’s almost scary. I told Littman after the next 22 of ‘CSI: Cyber’ we’re going to be at 802 (total ‘CSI’ franchise episodes). He said ‘OK, well, our goal is to get to 1000.’ Imagine.

Take us back to the beginning. What was your entree to Hollywood?

I wrote this (spec movie) called ‘The Runner.’ A buddy of mine, Dustin Abraham, when he first got to L.A. in ’97, he gave it to an agent at William Morris. Somehow it came back to me (in the mail) with coverage (attached) that said ‘No on writer, no on movie.’ I was like, wow that’s a bummer. But then when I first got to town the script was slipped to David Seltzer (then a manager at Addis/Wechsler and Associates) who brought it to the attention of Margaret Riley (Zuiker’s manager, now at Brillstein Entertainment Partners) and at that point she took me on a roadshow to talk to agencies.

Did you have any idea how the industry worked?

When I met with CAA they told me to meet them at Barneys. I was up at Barney’s Beanery waiting for (agent) Scott Greenberg. I called them and I’m like ‘I’m at the bar.’ It was like Abbott and Costello — the Vegas guy goes to Barney’s Beanery and it’s actually Barney Greengrass at Barneys New York. When I get there Scott has my script and says ‘This is really good, do you have another one?’ I said, ‘This is what I got.’ They signed me right there.

So CAA hooked you up with Bruckheimer to develop for TV?

At that time (Bruckheimer TV chief) Jonathan Littman was just starting Bruckheimer’s TV thing. I went into (Littman’s) office with lime-green index cards and talked to him about ‘CSI.’ He told me we had to get into this narrow window of pitching season. I said I needed to do my research. So I did my research and we got the pitch together and went to ABC. I did a really great pitch. Then they called and said they’d passed. That’s how my Dare to Pass company (name) was born. I couldn’t believe they passed. So then Littman told me Fox and NBC don’t want to see you because it’s October. He called up Nina (Tassler, then head of drama at CBS) and told her ‘I don’t know if you’ll buy it but this will be the most entertaining 20 minutes of your life.’

Sounds like you didn’t disappoint.

By the grace of god Nina Tassler in October hears this pitch. Jonathan told me ‘Don’t run around like you usually do because her office is small.’ And Jonathan told me ‘If you don’t sell it today it’s dead.’ So that was my motivation. (Tassler) told me ‘We’re going younger right now with a show we just bought called ‘Survivor.’ If you write me something great I will fight to get it on the air.’ I wrote the script in three days and the rest is history. You can imagine how the phone call went the other day after she announced she was leaving (CBS). I was sobbing on the other end of the phone and thanking her for saying yes back in the day.

Will you watch the finale on Sunday? Where will you be?

I’ll be in Buffalo (N.Y.) watching it with about 30 family members. They say don’t do that but I’ve seen it a bunch of times. I had final cut. All three of my viewing experiences have been satisfactory. I’m really, really blessed with the opportunity to be in this business and to really accomplish something that stays alive.

Do you think the time is right for the show to end?

Here’s the thing I always celebrate: It’s never over ’til it’s over. Nothing is sexier and cooler than Las Vegas. We have a timely format. There’s always a possibility to reboot, to come back to ‘CSI 2.0.’ There may be a time when that phone rings again.