[Warning: The following contains spoilers for Tuesday's episode of The Flash. Read at your own risk!]

The first full night of the CW "Arrowverse" crossover is complete, and one thing is totally clear — "Flashpoint" will go down as Barry Allen's (Grant Gustin) biggest mistake ever.

"Flashpoint" was a critical turning point for Barry in Season 3 of The Flash. It was a huge choice for him to decide to go back in time and save his parents from their respective deaths. It was an even bigger choice for him to decide to try and restore the original timeline, because the resetting caused fissures (and sometimes gigantic cracks) in the lives of those closest to him. However, the full extent of the consequences for his actions were swept under the rug after Episode 2.

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The ramifications of changing the timeline so drastically began to creep out with Caitlin's (Danielle Panabaker) Killer Frost powers and the schism between Barry and Cisco (Carlos Valdes), but the first installment of the "Arrowverse" crossover is making Barry face the music in a major way. Not only did the Arrow and Legends of Tomorrow crews find out what he did — and how it affected them — but the team also received an ominous message from future Barry warning them of how disastrous his decision was.

Now Barry is trying to lead a team against their most dangerous threat yet, but he can't convince any of them to trust him after he rearranged their lives. TVGuide.com talked to executive producer Andrew Kreisberg about what else "Flashpoint" has in store for Barry and whether the Scarlet Speedster will ever be able to make up for what he's done to his friends (and Earth-1 at large).

Grant Gustin, <em>The Flash</em>Grant Gustin, The Flash

Do you consider this to be the button on Flashpoint, or will there continue to be more ramifications?

Andrew Kreisberg: There's a villain coming up who's another one of the husk villains that was created by Alchemy, so there's that to deal with. But the midseason finale, Episode 9, kind of creates a new problem for our heroes that they weren't anticipating, something that they've never faced before. It's so big, we're actually considering changing the saga sell from talking about Flashpoint to talking about that, because that's really what's driving the episodes for the rest of the season, actually. Flashpoint won't loom as large as the challenge that presents itself in Episode 9.

Flashpoint has had such huge repercussions on all the shows, but it was only one episode [this season on The Flash]. Did you consider spending more time there?

Kreisberg: We talked about never going back, we talked about it being two episodes, we talked about it being five episodes. There was some input from the studio and the network wanting to make sure that we weren't upending our show in a jump-the-shark kind of way. I think that ultimately for us as storytellers, it was the right decision to have that one episode be It's a Wonderful Life but then I think people thought that oh, it's over with, and yet obviously the ramifications of him having done it will reverberate throughout not just Flash but the other series forever. Dig has a son now, Sara's gone. So we definitely discussed doing it different ways. The closest we came to doing something other than what we did was having it be two episodes, and the second episode just felt like it ran out of steam. The resolution with the parents didn't happen in one, it would happen in two, and it just felt like we were just putting things off that we wanted to get to, but that doesn't mean we've seen the last of it. Just because we didn't do it all in the beginning doesn't mean it's gone forever.

Could that message from Barry in the future be a direct thing from Flashpoint, or is he talking about more changes he makes sometime in the future?

Kreisberg: Um, uh, the message from the future relates to "Flashpoint," but it also may relate to something else coming up.

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The Wests were a much bigger part of this crossover than they were in years past. What made for that decision?

Kreisberg: I think one of the things we always try to do, especially with the crossovers, is not make it feel like all of a sudden we're in this evergreen world that's completely disconnected to everything that's been happening previous. At the end of [The Flash's "Killer Frost"], Wally became a speedster. That's huge. That's big news. To sort of gloss over that and not have anybody react — considering the myriad of reactions Joe has had to Barry becoming a speedster and Iris finding out — it felt like we'd be doing a disservice to the people who were watching The Flash and enjoying it.

We didn't want you to feel like, for the people that have been watching The Flash that suddenly their show disappeared for a week while we had all these superhero shenanigans. It was important to advance Wally's story. Also, this was a good opportunity to advance Wally's story in terms of — they all kind of got over their, "Oh God, Wally is a speedster," within the course of this giant episode where, what was the point of making sure Wally stays out of danger if the world is going to be destroyed by aliens? Him stepping into the fray and getting a little taste of things felt like it was an opportunity rather than something that we had to service because the story was telling us to.

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Now that HR is going to train Wally, how big of a disaster will that be?

Kreisberg: It will not go well. [Laughs] As assumed. But I think HR, what I love about this version of Wells, and he's said it himself before but we actually show it rather than just tell it, he is a genius in his own way. He's not a mathematical genius and he's not a physics genius the way the other Wells' were. But he has the capacity to see it in other people. And he has the capacity to see other people's talent and how to mine it and how to grow it. He sees that in Wally. Like he says in an upcoming episode, there's nothing in it for him to help Wally but he sees that Wally is special and that's where he can shine, in helping other people discover their own value and helping other people develop their own gifts.

It's an interesting relationship because a version of Wells was so important to Barry in Season 1, and a version of Wells was so important to Cisco in Season 2, and then this year it's Wally who gets this version of Wells that on the face of it, may not be the world's greatest teacher and yet every episode we find that moment for him to drop this wisdom bomb on everybody else that shocks them, and it's kind of why they let him stay around when he's not providing any actual true value to the team, that he really does have this value in keeping the team together.

Will there be further complications with Iris' byline no longer being on the "Flash Disappears" article from the future?

Kreisberg: It's going to have further complications.

The crossover event continues Wednesday night at 8/7c with the 100th episode of Arrow.

(Full disclosure: TVGuide.com is owned by CBS, one of the CW's parent companies.)