Everything about "The Flash" has been appropriately fast-paced -- with the exception of the unveiling of the central mystery at the heart of the show: why did the Man In Yellow murder Barry Allen's mother? And as the show moves closer to the big reveals of burning questions, the show's cast is hinting at a major upheaval in what the audience thinks is going to happen.

For example, viewers have been in on the secret that, despite having placed Barry on the path to becoming The Flash and forming a very warm and real-feeling role as his mentor, Harrison Wells is not really confined to his wheelchair, is pursuing a secret agenda with cold and ruthless efficiency, and appears to have been revealed as the villainous The Man In Yellow -- or, as comic book readers presume him to be, the Reverse-Flash -- on an inevitable collision course with the young Mr. Allen.

RELATED: "Flash's" Grant Gustin: There's a Surprise Reverse-Flash Twist Ahead No One's Seen Coming

But do viewers really know what Wells is all about? "No, you don't -- I'm going to guarantee you!" proclaims Tom Cavanagh, who plays the S.T.A.R. Labs scientist. Speaking with CBR News on the red carpet at Los Angeles' Paley Fest before a panel honoring the series, Cavanagh doubled-down on his statement with a big promise. "I'm going to sit here like Joe Namath guaranteeing the Super Bowl and guarantee there's a moment [coming up] where I am going to do something that's going to give you an idea of what I've been doing the whole season, and you're going to be like, 'No way!' You're going to be, like, head-smacking, gob-smacked when that that happens.

"It's been happening the whole time, and is a genuine surprise," Cavanagh added. "The reason I think you're going to be genuinely surprised is because when I read it, I was like, 'No way!' And I remember watching Grant [Gustin] when he read it. We were sitting backstage just hanging between scenes. He looked over at me and goes, 'No way!' I'm like, 'Yeah... Yeah.' There's moments like that aplenty coming still."

"There's a twist with Harrison Wells and the Reverse-Flash storyline that [nobody] has guessed," confirmed Gustin. "I've never seen it online. It's going to, I think, really surprise everyone. It's an original twist to the character that doesn't mess up the mythology."

The apparent reveal that Wells is the Reverse-Flash certainly shifted theories away from Iris' boyfriend, Central City detective Eddie Thawne, whose name is suspiciously similar to the Reverse-Flash's original comic book alter ego Eobard Thawne. And Eddie will be in the thick of action as the season races to the end, promises actor Rick Cosnett.

"Everything flips on its head for Eddie," Cosnett told us. "Obviously, there's been a lot of information held back from Eddie that he doesn't know yet. That starts to unravel, and there's a huge reveal -- there's a huge thing that happens with Eddie at the end of the season, and I think everyone's going to be quite delighted and surprised by it. I wish I could say more, but I'm dancing around the topic!

"I think, also, the love triangle with Iris and Barry and him comes to fruition," Cosnett continued. "Things happen quite fast. Eddie, obviously, knows that something's going on, but he's not really the jealous type. He's kind of the grown up in the situation, whereas Barry is the boy and Iris is the pretty much figuring herself out. But he also isn't one to just sit back and be walked all over. So yeah, it's very interesting what happens between him and Barry."

"A lot of questions that were left unanswered in Episode Nine," actress Candice Patton said of where her character, Iris, stands. "I know a lot of fans were waiting to hear about how Iris felt about Barry as well, and a lot of those questions will be answered in this upcoming episode."

And Iris will be caught up in the machinations of the Reverse-Flash as well. "Iris will come face-to-face with the Man In Yellow," Patton stated. "She will continue to investigate what's going on at S.T.A.R. Labs and Harrison Wells. She gets suspicious about Caitlin and Cisco and what their involvement is with Harrison Wells. She's just getting more and more inquisitive about what's going on in Central City and Barry's involvement in that too, and what that means."

Iris' dad and Barry's father figure Joe West also stands to see his relationship with Barry threatened after quietly investigating the shadier side of Wells. But as Jesse L. Martin points out, "Barry hasn't been entirely forthcoming with me, either, about what's going on, particularly when it comes to Harrison Wells.

"I'm learning a little bit more than he probably wants me to learn at this point," Martin added. "I'm a lot more skeptical of what Wells is doing, and how he's affecting everybody and everyone's relationships. Yeah, I feel like Joe might be a little in the dark, but not as much as Eddie or Iris. I'm learning as much as I possibly can."

When Wells' ultimate agenda is finally and fully revealed, of course, it threatens to completely upend the existences of the two characters who've been most steadfast in their support of the scientist: Caitlin Snow and Cisco Ramone.

"If Dr. Wells is not this perfect benevolent man who's been sacrificing his life to save the Flash and to help The Flash become a hero, it changes everything -- it turns the world upside down," Danielle Panabaker told CBR. "For Caitlin, in particular, she has always believed that Dr. Wells is an incredible, wonderful man. And the idea that, not only is he not perfect, but that he actually might have some malicious intentions would be devastating. "

"What's fun about playing Cisco is he's not just a funny guy all the time," actor Carlos Valdes said. "Even though he's very skilled at accessing levity in certain situations, he does have a bit of a darker side to him. I think you can start to see not just Cisco's but the entire team's emotions start to range from A to Z, basically, as things get discovered. Relationships get messed around with."

As all the plot points begin to align for the endgame, there's one piece of inside info that Cavanagh had no reservation about revealing, grinning as he described exactly how it felt to put on the yellow suit for the first time.

"One word answer: Tremendous!"

Reverse-Flash's plans begin to be revealed when "The Flash" returns tonight, March 17, at 8PM on The CW.