Don't go zooming ahead if you haven't watched the latest episode of The CW's freshman superhero hit "The Flash," because you'll be racing into a spoiler-filled landscape in which executive producer Andrew Kreisberg not only breaks down the key reveals and offers some behind-the-scenes insight into the course of the season's remaining storylines.

Everyone up to speed, so the speak? "The Sound and the Fury" not only offered the introduction of the classic Flash Rogue the Pied Piper, AKA Hartley Rathaway -- in the form of "Smash" actor Andy Mientus, playing the acid-tongued wunderkind and former protege of Harrison Wells (Tom Cavanagh) who resurfaces with sonic-based tech designed to settle an old score, it also offered an ultimately disturbing window into the agenda of Wells himself.

Mientus Sounds Off on Bringing the Pied Piper to "The Flash"

Seemingly humbled and uncharacteristically willing to reach out to mend the rift he's created between himself and Barry Allen and the rest of the S.T.A.R. Labs team, Wells is nevertheless revealed to still be just as cold and scheming as ever in his secret role as the Reverse-Flash -- and in possession of technology that channels the Speed Force to power him.

"We have this mystery where one of our characters is essentially the devil," Kresiberg explained. "He's mixed in with everybody else, and if and when people find out, what their reactions are to it and what their reactions are to other people who knew it -- that's the fun of this back half of the season." The EP joined a group of reporters to break down the episode's big revelations and to offer speedy glimpses at the breakneck storylines still ahead.

On showing the seemingly sympathetic side of Harrison Wells, while still illustrating that he hasn't veered in the slightest from his secret agendas:

Andrew Kreisberg: I think at this point in the storyline, obviously, the audience wasn't quite sure where Wells stood, and now, they have a little bit more of information about who he is and what he's up to. And now that the audience knows that, watching the camaraderie amongst everybody, it's almost more heartbreaking now -- and we just love that dynamic.

And there was just something just about the fun, especially the beginning of this episode -- that a little bit of "Keystone Cops," and Wells comes in and he's really, like, being this hero. But we all know that he's the Reverse-Flash. How do you square that circle? And that's one of the things that keeps changing throughout the course of a season as secrets start to come out. It's just like, how do you reconcile the Harrison Wells that we see in this episode, who's a friend and selfless and kind, with this monster? And I think that's why Tom loves playing the part. I think it's why we love writing the part.

On the target that's existed on Wells' back since the particle accelerator accident:

The truth is, every metahuman could wake up one day and go, "Hey, wait a minute -- It was that guy!" So we don't want to like play that card too often. And what was interesting about this one, and what made it different from "Power Outage" and Blackout was that Hartley hates him from before the accident. And Tom especially loves playing these pre-accident flashback days because he was playing this part and sort of living a sort of normal life. But you really saw a glimpse of that darkness when he lets Hartley go, so that was an interesting thing where it was somebody who was targeting Harrison for what he had done beforehand, and then consequently targeting The Flash because he felt replaced.

On translating the Pied Piper from comics to screen:

Well, like many of the comic book characters, they sometimes are a little bit silly. And the Pied Piper, dressed sort of very flamboyantly and literally, he would play his hand flute and warp people's minds. And we wanted to do something a little bit more grounded. And we were all fans of Andy's from his work on Broadway. And when we came in [Laughs], we said, "He is evil Harry Potter." And Hartley's not a metahuman; he's one of our technology-based powers, like Captain Cold. And they hadn't really gone up against anybody like him before.

We wanted them to go up against somebody who was brilliant and a genius and somebody that they had to really outwit, which was different because a lot of times, it's Barry either having to outrun or out-speed the villain. So this one was really complicated in that we sort of had to do a lot of different things. We had to establish an early on, how important Wells was to the team and how important his thinking was to the team. And that gave us the idea of the chess master. And as you saw, that played throughout the entire episode, that it was really a chess match with Barry as the pawn between the two guys... The endgame will happen this season. Yeah, Wells has a definitive plan, and when you look back, you will see he's had a definitive reason for doing all the things that he's done throughout the course of the season. And we think it makes sense. Hopefully, you all, will too.

Tom Cavanagh Talks Playing the Reverse-Flash, "Finally"

On the decision to let the audience in on Wells' identity as the Reverse-Flash before the other characters discover it:

I think with "Arrow," we kind of learned not to jerk the audience around too much. Just for Greg [Berlanti] and Marc [Guggenheim] and I on "Arrow," and for Greg and Geoff [Johns] and I on "Flash," I think sometimes people withhold secrets at their peril. And we felt like if we hadn't revealed it, then it wouldn't have been a satisfying conclusion to those first nine episodes. And the only debate we sort of had amongst ourselves was, how long will the audience accept knowing that he's the villain and having the rest of our characters not know? It was just something we'd been dealing with for the back half of the season. Are people going to feel like they're dumb for not realizing this?

And I think part of what's keeping these next stream of episodes going, is how good at hiding his villainy Wells is and how strong Tom's performance is. And having episodes like "The Sound and the Fury," where he really is being incredibly selfless and yet, part of you knows it's all a show and it's all fake, but just how effective it really is -- and even more so than that, how much you want it to not be true. I think that's sort of the biggest thing that we discovered as writers.

And when we watch the episode, you watch Tom in those scenes and you see how kind he is and supportive -- there's always those little moments throughout the episode, and just even moments that Tom brings to it, like throwing an ad-lib or the way he reads a line we weren't expecting or even just a look he gives. I mean, even though we know, we're the ones that made him evil [Laughs], we sit there and go, "Why? Why? Just please be Harrison Wells. Please don't be this nightmarish demon." But I think that hopefully, we've plotted it so that not being sure what he was and then knowing that he's the Reverse-Flash, but still not knowing what his full agenda is, people will have continued to invest in it without feeling like they're too far ahead of the characters.

On Joe's decision to look even deeper into Wells' past:

In an upcoming episode, Joe and Cisco launch -- without Joe letting Cisco know what he's really thinking -- a pretty spectacular investigation into actually what happened the night Barry's mother died, which plays out in a really cool way. It was actually one of our writers, Brooke Eikmeier, who came up with the very interesting piece of evidence which you'll see, I think, in Episode 13. But again, that was the interesting thing about this scene [in this episode]: It's like, Joe's being all, "Aw, shucks," but you see that he's there's something in his cop gut that tells him that this guy is wrong. And he can't let that go. Every time a piece of evidence comes his way, it gets dismissed, but Joe's Joe, and he smells something. That's definitely going to be causing problems for everyone, as the episodes progress.

On whether Joe's secret investigation will affect his relationship with Barry:

Every episode with a great Joe and Barry scene is gold. I mean, it just is. They're so good together. And you can see it. That love between them -- that's not only acting, but it's also between Grant [Gustin] and Jesse [Martin], and there really is this sort of father/son dynamic between them in real life, too, and that's sort of the heart of the show, and you don't want to mess with that. There's enough pain and heartache everywhere else.

I think one of the great strengths of "The Flash," the series, is just how close everyone is on the show, and they tend not to have these sort of raging conflicts like the way we keep giving everybody on "Arrow" [Laughs], because that show's more of a soap opera. And I don't say that derogatorily -- I mean, I'm one third responsible for it, the soap opera! But there, we always think to ourselves, how can we hurt these people more? And what's the worst thing we can do to Thea? And what's the worst thing we can do to Laurel? And what's the worst thing we can do to Oliver? And that's sort of where the drama comes from there. And I think part of the strength of "The Flash" is that the drama comes from how these people who have banded together and love each other and trust each other, how they deal with conflicts that come their way, as opposed to sort of list internecine conflicts that come... Joe and Barry, they're the rocks. And it's more about what they're going to do, as opposed to creating a schism between them.

Amell & Garber Prepare for Banter, Conflicts as "The Flash's" Firestorm

On the Pied Piper's impending return and his connection to Ronnie Raymond:

He's actually in the next episode. His threat that Cisco might let him out very soon and the repercussions of that will play out in the next episode... Caitlin's reaction to this information -- and also the knowledge that Cisco closed the door on Ronnie in the accelerator -- is both surprising and not at all surprising. And again, we're far more interested in these people getting closer and getting tighter, than we are in blowing up all our relationships.

On whether the TV incarnation of the Pied Piper has the same possibility for redemption as the comic book version has demonstrated:

Yeah, absolutely. And that was actually why we went to great lengths that he doesn't actually really kill anybody -- he tries to kill people, but there's no actual deaths. It's funny because we talk about that a lot with Helena on "Arrow" because we're slowly staging her, but she killed a lot of people and a lot of innocent cops. When we made some of those decisions early on, we weren't exactly counting on the longevity that we had. But with Hartley, definitely -- and especially with Andy who is so appealing. We booked him for two episodes, and are hopeful that he'll come back. And in the comics, he's in a relationship with Singh. So hope springs eternal.

On the impending introduction of time travel into the storyline:

If you've seen the pilot, you know in some subsequent episodes, certain individuals have certain knowledge of certain events that they wouldn't have if they didn't have access to the future. So yeah, if you're a fan of the comics, you know. "The Flash," ultimately is all about time travel. And you'll start getting some more hints of that. But hopefully, again, like I always say, we have to satisfy the comic book fans, but we also have to satisfy the regular fans. And for the regular fans, it's all brand new to them, so they're just kind of going with it. And for the fans of the comic, like trying to create and layer surprises that they're both having their expectations met, but then also having them subverted in a way that they enjoy and they're not angry at.

On introducing the Speed Force into the series:

Obviously, Speed Force is very important to the Flash lore. We don't have any sort of definitive -- right now, the Speed Force is, in a way, a little bit like the Force in "Star Wars" -- before midi-chlorians came along! But it is this amorphous thing. Hopefully, again for comic book fans, will make them feel a little bit more like we're heading in certain directions. For right now, it's a catchall phrase that sort of speaks to you, a grander universe and a grander power and ultimately, grander abilities. Because if you know the comics, you know what having access to the Speed Force gives you the ability to do.

On Barry's forthcoming romantic interest Linda Park, and Iris' reaction to his new relationship:

Malese Jow is so adorable. I mean, I can't -- we all just watched the screen. She's amazing, and she and Grant are really fun together. We wanted Barry to have a little romance, and our iteration of Linda -- she's a spark plug. She's a firecracker, and she's a lot of fun, and she's ballsy, and she speaks her mind, and she's cool. And Barry can't kind of believe that somebody like her is interested in him. [Laughs] And the episodes that have her, which I think is starting in Episode 12 -- and she's in four or five episodes -- she's really great. And Barry suddenly having somebody like that in his life will cause all the other women in his life to maybe see a little green.

[Barry and Iris] sort of had that really nice talk in episode 10, but [his feelings are] out there. And I think that when he starts dating Linda, [after] Caitlin said, "You change things" -- he's putting it out there. And it's definitely weighing on Iris and it's going to weigh on Eddie -- and it's going to weigh on Caitlin. And it's going to weigh on Linda, a little bit. And watching what putting that out there means is a lot of the emotion of the back half of the season.

Routh, Rickards Head To "Flash" For "All-Star Team-Up" Episode

On the upcoming crossover that brings Felicity Smoak back to Central City, along with Ray Palmer:

At that point, Ray needs a little help with his suit, and who better than Felicity's high-tech guys at S.T.A.R. Labs? It happens to come at a particularly bad moment for Barry, but that's partially why we did it. The first episode with Felicity -- Episode Four -- she really helped come along at a time where her experience in being part of a crime-fighting team definitely helped Barry overcome what he was facing that week. And similarly, when she comes back, he's having a crisis of conscience that, in some ways, only somebody like she can help him through.

But it's a really fun episode. I hadn't gotten to write much Ray this season on "Arrow," and I got to write him in the comic book, in the "Season Zero" [comic book] that we wrote, and I loved it. So getting to write him, he's just so much fun, and he finds a best friend in Cisco. There's even a line in the script where Felicity says, "Ray is like Barry in Oliver's body," and then went, "Oh God -- did I say that out loud?" Ray, even though he looks like Brandon Routh, he's just a big tech geek at heart, so he and Cisco quickly bond. And it's just a fun episode. We have the Bug-Eyed Bandit, a big Atom villain, is going to be the villain in it.

On keeping the Central City team in the dark about Oliver Queen's disappearance over in "Arrow":

When you do these things, when you have these shared universes, sometimes it's the coolest thing ever, and there's an upcoming thing in a "Flash" episode which feels like a throwaway, but it actually describes an event that happens in a flashback story this season on "Arrow." And we do stuff like that. For us, it's so much fun, and hopefully, the audience finds it fun, like last season, all the mentions of the accelerator on "Arrow" and Channel 52.

And then sometimes, it's a real hindrance because even in the room, we're like, "Oliver's missing -- call Barry. Have him run to Nanda Parbat and run all over the place until he finds him." So sometimes when it serves us, it's absolutely great. But the more we talked about it, sort of bringing all that up on "The Flash" side of things, especially given all "The Flash" stories and knowing that Oliver is missing, it sort of created more problems than it was worth because it's like if you address it on the show, then they seem a little bit unsympathetic that they're not throwing all of their S.T.A.R. Lab resources to finding Oliver.

So sometimes, discretion is the better part of valor. But Ray and Felicity are coming. And because the airdate's changed, we're trying to square the circle on what was happening on "Arrow" when they come to "Flash." So hopefully, it won't feel like too much of an evergreen episode, because we felt like it really worked the first time around.

On when, after so successfully introducing the key Rogues, the show might bring them all together on screen:

I think this season is really about introducing them all. We have Episode 16 which is we're going to have Captain Cold, Heat Wave and Lisa Snart -- Golden Glider. And obviously, we've got the Trickster in Episode 17. Those dailies are incredible. Yeah, I mean, we're going to do something with all the Rogues. I can't promise that it will be this season, but definitely. We know that the original "Flash" series, if they had gotten a second season, both John [Wesley Shipp] and Mark [Hamill] have told us that the first episode was going to be a giant Rogues episode. So that sounds like maybe a good thing for us to do, what they didn't get the opportunity to do.

"The Tomorrow People's" Peyton List to Join "The Flash"

On casting the Golden Glider:

That was another sort of no brainer. I didn't work on "Tomorrow People," but I was working with Greg while it was all going on, and Peyton [List] is that rare bird of being so unbelievably gorgeous but also being so unbelievably talented. And she was just right at the top of the list. And she's also really funny, so it felt like she would really fit in there. And I know Wentworth [Miller] and Dominic [Purcell], especially the two of them, with the history that they have and the shorthand and the in-jokes and the camaraderie, if you were going to throw somebody in there, it had to be somebody like Peyton, or they were going to get blown off the screen. And she certainly stands toe-to-toe with the two of them, and it's a really fun relationship.

Watching him try to be a good big brother to this slightly psycho younger sister, and watching her manipulate Heat Wave -- and Dominic's willingness to be a dumb lug for love. I can't say enough about him. He loves playing the part, and the three of them together, it's just so much fun to watch. And again, you're seeing that dynamic of -- because you haven't really seen that anywhere in live-action -- watching all the villains team up. On both of our shows, we've got Team Arrow, and we've got Team Flash. But watching the Rogues form, and the complexity of those characters and the caliber of actors that we've gotten to play them, you can envision an episode where you're just following them, and you're not bored.

On having enough singing talent to make "The Flash: The Musical":

We're getting crazy with the number of people who can actually sing on this show. In the next episode, Episode 12, we actually get to hear Grant sing, which is a real treat. Grant's a very good singer. Danielle [Panabaker] said, "I can't really sing." And I said, "As bad as you think you are, you have to sing worse than that." Barry and Caitlin go on and an inadvertent date, which is one of my favorite scenes of the whole year. They're hilarious together. And it's funny, because Jake Coburn is one of the "Arrow" Co-EPs. He came by, and I was watching it and he's like, "Yeah, scenes like this [are] where 'Arrow' goes to die." The characters going out for a drink or characters going out and having fun. Whenever we try that on "Arrow," it never works, and we cut it. Or, unfortunately, it aired. But it's fun with "The Flash": you really can sort of have these, like, after-work- everybody-goes-out-and-has-a-drink-and-has-a-fun-night [scenes].

On the subject of cut scenes:

Greg and Marc and I actually worked with Victor Garber on "Eli Stone" which was a show that we all worked on together, and when we started talking about doing Firestorm -- there's a scene in Episode 13 which was actually in the pilot. We were going to have Barry on the train home from Starling City, coming back to the Central City pilot, and we were going to show him on the train and meeting Martin Stein. And we just decided, for time and budget, that we didn't quite need it. But even back then, we were saying that we should get Victor. So this has always been in the back of our minds, and I don't know what kind of stars we were born under, but it feels like every time we have one of these amazing parts, our first choice somehow agrees to do it.

On kicking off the second half of the season with a bang:

Having not always come back from "Arrow," I think both of our Episode 10s -- and it's no disrespect to the writers and the directors and the cast -- we didn't always feel like we came back as strong as we could have from the Christmas break on "Arrow" on Seasons One and Two. And so we were really conscious on both shows: "What can we do to come back really strong?" And having that incredible cliffhanger on "Arrow" certainly helped.

But creating this sort of trilogy of episodes with Brick was certainly something that we'd never done before, sort of having this mini-Big Bad in the middle of the Big Bad to really make those episodes strong. And then with "Flash," we were like, "Our greatest villain so far has been Wentworth, so to have Dominic come out with the first team of the Rogues and Cold and Heat Wave versus them -- we thought that was such a great way to come back. And then going to Pied Piper: it wasn't a conscious decision to move away from that. We've got a bunch of meta-humans coming up. We've got Peek-a-Boo in Episode 12, and Firestorm in Episode 13, and Weather Wizard -- the true Weather Wizard -- coming up.

"The Flash" airs Tuesdays at 8pm on The CW.