We've suspected for a while that Nora (Jessica Parker Kennedy) has a partner in her little mission in the past, but now that The Flash's 100th episode finally revealed who it is, we only have one question: Girl, what the hell are you thinking?!

In order to take on Cicada (Chris Klein), Barry (Grant Gustin) and Nora decided to travel back to important moments in his own past to gather the crime-fighting items they need. This trip took them back to witness confrontations with Zoom (Teddy Sears), Savitar and even the Reverse Flash (Tom Cavanagh), whom Barry had to ask for help (again). Though the plan to take on Cicada didn't end up panning out, it did force Nora to turn to the person who's apparently been helping her with this trip to the past all along — Eobard Thawne!

In the daunting scene that revealed Nora's partner, Thawne appeared to be housed in some kind of cell, which is mildly reassuring, but the fact that Nora is working with the Reverse Flash in any capacity seems like bad news for everyone involved. Not only is she lying to her family about working with her father's nemesis, but she's actively working with a guy who lies every time he takes a breath. This can only end in tears!

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Something tells us a timeout is on the way when Barry and the team find out what she's up to, because as Hartley Sawyer told TV Guide on the red carpet of the 100th episode celebration, this is going to be a "big game-changer."

"There's sort of going to be a line in the sand drawn from everything that predates that to this," he said. "The fallout from this is going to be something that's catastrophic."

Catastrophic sounds about right, but Grant Gustin thinks that no matter how betrayed Barry might feel when he finds out his daughter's secret, he still thinks their father-daughter relationship can weather the storm.

"I think there will be a blowup, but I think we'll be able to pretty easily put the pieces back together," Gustin said. "I don't think it will ruin the father-daughter relationship."

"I think at the end of the day, Nora, whether she's good or bad, she thinks she's doing the right thing," added Jessica Parker Kennedy.

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Admittedly, it's hard to imagine the spunky, adorkable daughter of our two favorite characters being full-on evil — even if The Flash has become known for crushing reveals like this. Even growing up without her dad couldn't have put someone as sweet Nora on a totally dark path, so we have to believe she's using Thawne in some way to help save her dad from his fate.

Unfortunately, we can't see that working out very well for Nora. Once Thawne gets in your head, you only have so long before you find yourself up the creek.

The Flash airs Tuesdays at 8/7c on The CW.

(Full Disclosure: TV Guide is owned by CBS, one of The CW's parent companies.)

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Grant Gustin, <em>Arrow</em>Grant Gustin, Arrow