Get ready for an eyeful — and an earful — of Nathalie on Sunday's Quantico.

The NAT's backstory involving her ex-boyfriend and daughter will finally be revealed, along with, as previously reported, the truth behind her fake ear scar that — reminder — no one can see. But Nathalie (Anabelle Acosta) should've invested in some superglue because the scar falls off in the field, and Miranda (Aunjanue Ellis) calls her out on it in front of the whole class.

Miranda's awfully pissed about something as minor as a fake scar, no? But for Nathalie, the reason for the scar is serious and ties back to her turbulent relationship with her ex and father of her daughter. "Her secret is one that has a lot of heart in it. Her secret is not that one is malicious," Acosta says. "I think the reason she chose to wear that fake scar will make sense to a lot of people. ... To a degree, there's some shame to it because it's a lie and she's obviously trying to be about truth and justice, so it's still shady. There's a very, very good reason for why she did it and they're human reasons. They're maternal reasons. They're reasons that she felt could protect her daughter and protect her in a situation with the man she was involved in."

Quantico: Someone's looking a little guilty

In last week's episode, Nathalie confessed to Shelby (Johanna Braddy) that she was in a bad mood because it was her daughter's birthday, and she's regularly conflicted about whether she made the right choice to join the academy. That's partially because her ex is guilt-tripping her about that too. "Some men do that to their partners, and I think the episode addresses that it's not so much physical abuse but emotional abuse," Acosta says. "I feel emotional abuse leaves scars just as deep as physical abuse." The actress' hope is for fans to come out of the episode with a better understanding of, if not sympathy for, Nathalie because that perma-scowl doesn't make her a "total meanie."

"It's a beautiful episode because it makes her very human," she says. "Mothers are going to relate to her a lot, and any woman who's been in a situation where she has to leave her child or dealing with emotional abuse with a man, feeling like they can't leave, and having the kid involved and having a career, women who've felt like they have to choose between family and career. We have women who can do it all. ... I think a lot of her bitterness and toughness come from things that have hardened her, situations that have really hurt her. We get to see her in a very human light versus the Nathalie who's been picking on Alex."

Well, she's not picking on her anymore... for now. Last week also saw Nathalie join Team Alex after they all found evidence (literally in plain sight) that Alex (Priyanka Chopra) was framed for the bombing in the future. Until then, Nathalie was one of the refreshing few who wasn't on Alex's side - though she did let Alex and a wounded Ryan (Jake McLaughlin) go a couple weeks ago, which Acosta chalks up to her romance with Ryan.

"I think she chose with her heart in that moment. That was a heart over mind decision. But there's a part of her that questions if Alex is guilty or not," she says. "I don't think at that time she was 100 percent confident that Alex is guilty, and I don't think she would've taken them both in unless she was sure. And there's all this evidence she might not be coming to light."

But is Nathalie fully on Team Alex, given their stormy history? "She has that tension with Alex because she wants to be the best at what she does, and Alex is the one who is in the way. It's not even about Ryan. But I think at the end of the day, Nathalie takes her job seriously and I still think she does what's right," Acosta says. "She would be one of the last ones to fall in line in helping her ... but I don't think she's vindictively thinking about taking her down from the inside. She's like, 'I don't like Alex, but what are the facts? What's the evidence? Why are people defending her?' I think she's able to separate those two things. She's very much about her job and doing the right thing."

Quantico airs Sundays at 10/9c on ABC.