[Warning: The following post contains spoilers about 9-1-1's Season 3 finale, "What's Next?" Read on at your own risk!]

Buck (Oliver Stark) needed closure when it came to his former relationship with Abby Clark (Connie Britton), and on Monday night's eventful Season 3 finale of 9-1-1, he got some closure all right. Not only did Buck get the chance to finally ask Abby about where she's been, but he also got to be her personal hero one last time — rescuing her fiancé at great risk to his own life.

Titled "What's Next?" 9-1-1's Season 3 finale brought Abby back into the fold of the disaster procedural as her train from Phoenix to Los Angeles was derailed, with multiple casualties. Her fiancé was one of the passengers who was stuck in the last car, and it was only thanks to Buck's bravery (and foolhardiness, of course) that the man was rescued from certain doom. After the dust settled and everyone was secured, the two then had a heart-to-heart in which Abby explained that she needed to go away to find herself and feared that if she came back to him, she'd lose herself again. In the end, Buck understood her reasoning and made peace with her new life, even complimenting the man she's going to marry.

Elsewhere in the episode, Hen (Aisha Hinds) saved a boy who'd been internally decapitated, and she sailed through her practice MCAT; Michael (Rockmund Dunbar) got the good news that his tumor was in remission; Athena (Angela Bassett) threw a party to celebrate May's (Corinne Massiah) graduation and grappled with how her near-deadly confrontation with the serial rapist might affect her career; Josh (Bryan Safi) prepared for his confrontation with the man who beat him and took him hostage in the dispatch siege episode; and Maddie (Jennifer Love Hewitt) discovered that she is pregnant with Chim's (Kenneth Choi) baby. All in all, Season 3 ends on a relatively hopeful note for almost everyone involved!

TV Guide caught up with executive producer Tim Minear to talk about how Britton's return came together and what it means for Buck in the future, as well as his plans for Season 4 and a potential crossover with the show's spin-off, 9-1-1: Lone Star. Read on for Minear's thoughts.

Oliver Stark and Connie Britton, <em>9-1-1</em>Oliver Stark and Connie Britton, 9-1-1

Can you tell us the story of how Connie Britton's return to the show came together?
Tim Minear: Yes, it's a slightly anticlimactic story, but I like it! We were sort of in the middle of the season, and somebody had pitched — I think it was Chris Monfette, a producer on the show — "Wouldn't it be great if in the penultimate episode before the finale, Maddie gets a 9-1-1 call from some disaster — let's say, a train derailment — and the woman on the other end of the line seems to know a lot about the protocol. And we reveal it's Abby, and she's calling from this train derailment; she's on her way to L.A. from Phoenix, where we've established her brother lives." And I was like, "Well, that's a great idea. It'll never happen. I've been trying to get Connie back for a year, and now we're in Season 3 ... although she had finished Dirty John, so maybe she'd be available?"

Well, it just so happened that, I think maybe the next day, it was the 100th episode party for American Horror Story, which was over at the Hollywood Forever Cemetery. And so I show up at this thing, and of course there's Connie. She was the star of Season 1. And I'm standing there talking to Angela Bassett, and I'm like, "Let's double team her!" So we went over to Connie, and I said, "Look, why don't you come back and guest on the finale?" And she said, "Oh, I'd love to!" And so that's how it came about. It was that easy.

Did you have to retrofit the rationale for Abby leaving in order to fit her back in, or is that what you guys always envisioned had happened to her?
Minear: I think the fact that she came back with a fiancé was the thing that made the most sense in a lot of ways. But we were very specific and particular in Season 2 to not drop the Abby story even though we didn't have Connie Britton. So a lot of Buck's story from the first half of Season 2 ... was him still living in her place. I mean, a lot of this — it's interesting because a lot of things you do because production necessitates it, right? You lose an actor who has only signed on for a year, and she's going off to do something else, so she can't be on your show, you can't afford to build a new set for a character, so he stays in Abby's house — it's the set that I own. So it sort of became the story. Buck is living in a relationship with a ghost. And he doesn't realize the relationship is over until long after everyone around him does.

So that's kind of Buck's story, and I always felt like he needed a moment for her to come back, so that he could say, "What the hell happened?" And we understand that he was the catalyst that allowed her to go off and "find herself." It's just that the person she found was not the person who left. Which is generally what would happen if you need to find yourself. And for Buck, I think that he was starting to build a myth in his head that this relationship had fixed him when in fact it had course-corrected him and that his own growth is his own agency and something that he can take credit for and move forward. That, for me, is what that parting moment on that bench is all about, and why I thought it was important. And if it'd come any later than the end of Season 3, it probably would've been too late and moot at that point.

From here, since now he has that closure, do you think we'll finally get to see Buck in his romantic element again?
Minear: Yes.

Well, that should be fun. Can you say what May wanted to talk to Maddie about after she brought up USC?
Minear: I can! But I won't.

With Maddie, the hostage situation at dispatch was one of my favorite episodes of the season, so it was really fun to see Josh face down Greg. Do you think Athena will get to have a similar confrontation with the man who attacked her?
Minear: I would not be a bit surprised, and I think that Brooke Shields' character might help her with that.

It seems like a lot of the characters this season faced and triumphed over traumas this season, including Buck, Maddie, Athena, Chim, Eddie, Bobby, Hen, and Michael. Who should we be worried about going forward?
Minear: I think you can worry about all of them on some level. Yeah, it's true. We didn't go out of this season like Buck had a fire truck on top of him at the end of last season, and he wasn't even sure if he would be able to continue his career. I wouldn't worry yet. What I really wanted to do was end the season on an up-note for everybody. So you just never know when the next thing's going to hit. I mean, I'd be worried for Rob Lowe.

There you go. So speaking of Rob Lowe, now that both shows have been renewed for the next seasons, are you guys starting to think about crossover plans for the two shows?
Minear: Yes, I think we will definitely avail ourselves of that opportunity.

Thinking about Season 4, are there any themes or disasters that you really want to do next?
Minear: Right now, I'm trying to come up with something that will live in the same column as a tsunami or an earthquake. It's difficult. I mean, I think one thing people come to expect from us is kind of that Irwin Allen summer thriller disaster movie. So if you have any ideas, you have my email. But it's always a challenge to come up with new cases and new themes. I think what we're lucky with is that we have now built worlds with these characters that we care about, so now we're trying to figure out what are the most interesting themes for their lives ... As far as the big cases, there are a couple of big cases that I'm very interested in that I'm still trying to figure out how to do. You know, if you'd asked me this same question at the end of last season, I did not know I was doing a tsunami until maybe a month into the writer's room.

With Hen potentially going to medical school, is there a chance we could see the 9-1-1 series expand into the hospital setting a bit more?
Minear: Maybe here and there, but I just don't think that's what we do. I mean, you can use this against me later if that changes, but I think we're not Grey's [Anatomy], we're not really a hospital show, although we have a hospital set, and we're often there. Typically, it's because somebody got rebar through their head or they got stabbed ... those are the reasons we end up in the hospital. So I think Hen's journey is an interesting one, and I think the thing that interests me is less about the hospital setting and more about this woman who at this stage at her life is not willing to stop growing and becoming more amazing.

Looking back on the season, what for you were some of the biggest highlights?
Minear: I will not lie, the tsunami was kind of a crowning achievement for us — just physically creating that production, going to Mexico, building [it] ... everybody on production and the actors and the writers just really topped themselves in those two episodes, and they were very different.

I thought that "Rage," the episode where Michael is pulled over by the potentially racist cop, I thought that conversation he has with his son was a very [important] moment for me in the season, and I also loved the call center being taken over — if for no other reason than that was pitched to us by a new staff writer this year who for 21 years was a 9-1-1 dispatcher who said that her fear was always somebody would come in and take the place hostage because they were the cerebral cortex for where the police would be. So if they wanted to do something dastardly, that would be the place to take over. So as kind of big and blockbuster movie as that idea is, that came from a real-world place from a person who actually had experience with that.

What was really fun about that episode was it broke tradition of the show with the reveal at the end that elevated the mood to this fun, Knives Out-style whodunnit.
Minear: Yes! We sort of did a similar thing with "Ocean's 9-1-1" the year before, but that is the thing I really adore about 9-1-1 is you can do — and I don't say this in a disparaging way — but you can do the Lifetime movie of the week of Maddie being abducted by her insane husband and sort of that woman in jeopardy taking her power back, you can do that story. You can do a caper. You can do an Irwin Allen thriller. Or you can do a romantic comedy like "Buck Actually." We can do anything on this show, and that is what is so great for our show.

9-1-1 has been renewed for Season 4 by Fox and is expected to return in the 2020-2021 midseason.

Connie Britton, <em>9-1-1</em>Connie Britton, 9-1-1