When the wheels go up on Season 14 of “Criminal Minds” on CBS, the series won’t just unroll a new slew of cases and delve deeper into its roster of characters’ personal lives; it will also celebrate a landmark 300th episode.

The episode, aptly titled “300,” picks up a few minutes following the Season 13 cliffhanger finale, in which Reid (Matthew Gray Gubler) and Garcia (Kirsten Vangsness) were at the mercy of a deadly cult. But it also features a killer who has 300 murders under his belt, the return of Luke Perry as deceased cult figure Benjamin Cyrus, and flashbacks to when viewers first met each of the current team members.

“After 300 episodes a lot of people feel like they’ve seen it all, but this they’ve never seen,” showrunner Erica Messer tells Variety. “The team’s mission is to find two of our heroes without being able to use the super power of those two heroes. It ends up being a really great ride for these characters — certainly Garcia, who has never been taken captive like that — to be on.”

Here, Messer talks with Variety about keeping a show alive throughout a rotating cast of characters, evolving viewer habits and spinoffs, and the ultimate path to 300 episodes.

How did the idea of a killer who killed 300 times come across your desk?

I wondered earlier on in Season 13 if that would be possible, so I did some research and it’s actually not that crazy. It’s happened before. The way we were ending our season, episode 299 allowed us to make that come to fruition. It’s really wild what has happened in this world. When you dig into whether something like this is possible the answer is yeah, it is. I’d like to believe it isn’t, because we have an elite team of profilers who would catch somebody before 300 people die, but we’re able to answer that in a believable way as well — why the team hadn’t solved this case in all these years.

How does the return of Luke Perry, whose character previously died, factor into the premiere?

What we do in terms of trying to solve how 300 people have been killed and we didn’t know about it, is we have to dig back into our own history and that history leads us down the path of Luke Perry’s character and his beliefs. Knowing that history helps us solve the present-day crime.

After 300 episodes, how did you land on which guest stars to try and bring back?

Picking up from 299, there were things that would have just gotten in the way of telling the history of the series. Instead we wanted to focus on the big task at hand: getting the team members out of jeopardy. It felt like we just had to focus in on the one that would make the most sense to conclude our story. That’s why we didn’t bring other characters who have been on the show back — there was no time for it. It was an efficiency model, really.

The episode launches Garcia down a certain path, but how does it set up the rest of the season?

The challenge is to make this new team feel as solid as the original team. That was our point here — everybody gets to have a heroic moment in “300,” and it’s all for the greater good of keeping our team together, and that will continue to play out for the remainder of the season. We’re going home with a character pretty much every week for the first nine or 10 episodes because that’s how you get to know the team better and get a new insight into what makes them tick.

At this point is there an audience appetite for breaking episode format like that or is it an earned risk?

There is a format but there are plenty of times we’ve broken it — and we did that early on. Around episode 15 of the first season we opened up the episode with our team in SUVs driving to Florida to interview a husband-wife serial-killing team before he’s put to death. That broke the mold of what we had given everyone. Those kinds of episodes are what make people come back. In “300” we do flashbacks. We even open the show with a series recap in a way and show every character that’s currently on the show back when the audience first met them. Even that little thing is a nod and thank you to the fans for watching all this time. And in that recap there is never-before-seen [archival] footage of a character. It’s just a really small bit in the series recap, but those kinds of things are important to tell in the passage of the years spent telling these stories together.

Given the way consumption habits have changed does it make more sense to play with the format for nine or 10 straight episodes now than it would have in the past?

It probably does. When we first started the show, streaming wasn’t a thing so you didn’t really expect people to binge a boxed TV set. They did, but you didn’t really create a series based on that. Today you do think about that. If somebody is sitting down and they’re watching it all back-to-back, [we think about] do we have too many of this kind of story over the season or do we need to split those things up a little bit? This year we inadvertently have a few stories where there’s kids involved at the core of the case, and that’s something in the past we might only do once a year, if at all. This year we ended up with three different episodes in our 15-episode order, and so we didn’t want them to be back-to-back for the streaming purposes of the show. We have such a new audience finding the show now; there are kids watching now who were born when the show came out. My son was one when the show came out and now he’s a freshman in high school and his friends are watching. Because of the ability to binge we’re finding that young audience all over again but the loyal fans who have been watching us every Wednesday night for years are still tuning in.

How has the research process in terms of serial killer stories you find for inspiration changed since that original season?

When we started, no one had written a show about serial killers before. We all had our foundation of like, “Silence of the Lambs,” and we were all aware of maybe a handful of killers like Ted Bundy, Jeffrey Dahmer, The Zodiac Killer, Jack the Ripper. You knew of serial offenders. But after those first 13 were done we had to dig much deeper and it turns out that it feels like an endless supply. There are books about serial offenders, and we also have an incredible resource in the FBI itself. We have a few consultants who tell us about cases they had worked on that aren’t in any books. All of a sudden this wall of bad guys — these stories — were endless. And weird things would happen. Years ago [executive producer] Breen Frazier was writing this story about a kidnapped girl, who was having children in captivity, and then Jaycee Dugard’s story came out. It broke in the news while we were shooting the episode. These real life things were happening out there. The Ariel Castro case in Ohio — we [were] writing about some weird stuff, but it was already happening in the world. Some people will sometimes ask if we’re afraid we’re inspiring this stuff. I’m not afraid of that because from my side-chair profiling, somebody either wants to do harm or they don’t want to do harm. It’s not anything we’re encouraging in any way. Who made Jack the Ripper do it? It wasn’t a TV show. It wasn’t a movie. What we’ve studied about human behavior is that there are many things that have to happen. It’s nature and nurture and stresses and triggers and all of these things that have to come together, and usually it’s part of some kind of mental illness. If you don’t have those things, watching something is not the thing that’s going to make you do it.

Does being a mother and female give you any storytelling edge when running a show revolving around a world of predominantly male serial killers?

One of the constants in the world is that a majority of serial killers are men and a majority of the victims are women and children. Most of the time it’s men attacking women and children. We have tried to make an effort to have more female killers, and to have the victims be equal opportunity. It’s not necessarily what statistics would tell you, but for our purposes killing women every week is not great. A lot of showrunning is parenting. Ed Bernero, who was the showrunner before me, is a dad with three kids. They were out of the house by the time I met him, but we would talk about that stuff all the time. It brings an honesty and a vulnerability to the storytelling. There’s a quote we have in an upcoming episode that “When you have a child, the world has a hostage.” I don’t know if it adds an edge, but it adds an honesty.

“Criminal Minds” has been reported as a bubble show for years — would you have done the cliffhanger finale last year if you felt there was real danger of cancellation?

I’m not necessarily a big risk-taker in life, but every year … we’re not the show that gets the early pickup. We’re always last-minute and a lot of that is just business because we’re an ABC Studios show for CBS network and they’ve always got something to work out. But one thing I do feel good about is we are a consistent player for CBS. When I see how we do with the younger audiences in streaming, all of those things make a difference. I did feel like at the very least CBS would have allowed us to wrap that storyline in some way like they did with the two-hour movie to end “CSI.” At the very least I was banking on CBS’ prior behavior. It was a risk, but I felt like there would be some satisfactory ending.

You’ve sustained numerous cast changes over the years. At this point is there a member of your core cast without whom the show could not survive?

We’ve certainly had our share of changes, but I would argue any show that’s been on this long does. Certainly the biggest test to our ensemble was when Mandy Patinkin quit in Season 3. Without him, did we have a show? We didn’t know. We hoped so. We felt, behind-the-scenes, that we had a lot of strong characters that could keep the show going. And that’s what happened — the viewers got behind the remaining cast and we wrote to the emotions that we felt after he left and wrote it into how the characters felt that Gideon left. We ultimately dealt with it and moved on. The viewers stood by and we kept going. When that happens so early in the life of a show, it proves the show is bigger than any one person. Everybody has their favorite character and that character might not be there anymore, but there’s a greater admiration for the team as a whole and that keeps people watching.

What does “Criminal Minds” have that resonates with audiences that its two spinoffs maybe didn’t?

Some of that goes back to knowing characters for so long. When “Criminal Minds” started in 2005 it was an ensemble and it’s a lot of work to let the audience know every character. The second season we dove in more and then by the third season we were cooking with gas. Both spinoffs — although “Borders” got an additional midseason — only had 13 and 26 episodes for audiences to fall in love. I would argue that not everyone fell in love with “Criminal Minds” really until midway through Season 2. That’s over 26 episodes. Part of it is that, and part of it is that audiences like to believe there’s only one team out there that does this. I tried to change it with “Borders,” but ultimately they like this skill set to belong to one group of people, and that’s the people they’ve been watching since 2005.

“Criminal Minds” returns Oct. 3 on CBS.