Jennifer Grey is making her anticipated debut on Grey's Anatomy -- and she's desperately seeking answers.

On Thursday's episode, titled "I Walk the Line," the Dirty Dancing star drops by Grey Sloan Memorial Hospital searching for the truth about her daughter, Betty (real name: Brittany), and only ET has the exclusive sneak peek at Grey's intense introduction.

In the exclusive clip, Betty's real parents, Carol Dickinson (Grey) and her husband John (Kyle Secor), meet Amelia (Caterina Scorsone) face to face for the first time to try to get to the bottom of how Betty -- sorry, Brittany -- was able to pull off her elaborate lie. But, as Amelia quickly learns, they don't know the whole story.

For the past several months, Amelia has taken Betty under her wing, helping the recovering addict cope with her pill addiction, and even sending her to rehab. In the most recent episode, Betty came clean to Amelia about her identity, revealing that her parents are unaware of her whereabouts and that she has a baby boy named Leo.

"We started driving to the rehab center right away. We just were so happy she was alive," John tells Amelia, after they share that Betty gave them a call two days prior. 

"They gave us your number and they said that you were her legal guardian?" Carol asks, not quite understanding how that's possible. 

"She's been living with us for a few months now. I tried to call you several times. I thought I was calling you... She gave me a fake number," Amelia says.

But this is all too much for Carol to process, who begins to grill Amelia on how she could have found herself in a position where she was able to even entertain guardianship of any sort.

"She came in for a doctor's appointment for Leo, and she was trying to stay off drugs for him. I could see she needed help and so she just became a part of our family," Amelia explains, expecting Carol and John to know who she's referring to. They don't. 

"Who's Leo? Is that her boyfriend? Is that why she never came home?" Carol asks, not knowing how dead wrong she is. Oh, things are about to get messy. 

Grey's Anatomy airs Thursdays at 8 p.m. ET/PT on ABC.

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