Patricia Arquette isn't afraid of taking on a dark and haunting true story.

The Oscar-winning actress walked away with a Golden Globe, a Screen Actors Guild Award and a Critics' Choice Award last year for portraying Tilly Mitchell in the Showtime limited series "Escape From Dannemora," about the prison break in update New York.

Now, she's back in another true crime series, "The Act" on Hulu, which tells the complicated and shocking story of Dee Dee Blanchard and her daughter, Gypsy Rose. Blanchard allegedly suffered from Munchausen by proxy syndrome, a mental illness where a caregiver purposely causes harm or illness to another person under their care — usually a child, elderly or disabled person.

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Arquette told Fox News she needed to find the humanity in Dee Dee in order to play her. "I really think that Dee Dee [was] mentally ill," she told Fox News at the premiere event in New York City.

"I also think that Dee Dee has an aspect that we all have — co-dependence, fear of abandonment, concern for her child — but her intensity is out of control.," Arquette added. "She takes it to a really toxic level."

The most important relationship – on which the entire show is based – is the one between Arquette and Joey King, who plays Gypsy. Their chemistry was immediate, Arquette told us. "It was really weird, Joey and I just kinda had that chemistry the whole time. I felt like she was my daughter. We have the same sense of humor."

It wasn't easy to find someone to play the role of Gypsy; one of the series' executive producers/writers, Nick Antosca said it took a long time to find King. "We auditioned a million girls for Gypsy and then we saw Joey," he told us. "He said he specifically had Arquette in mind for the project."

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Another actor from the show who dove head first into the role was Calum Worthy. He plays Nick Godejohn — Gypsy's boyfriend and accomplice in the murder of Dee Dee. Godejohn is currently serving life in prison without parole after being found guilty of first-degree murder, while Gypsy is serving 10 years in prison for second-degree murder.

"I became a little obsessed," Worthy told Fox News of prepping for the role. "It kinda took over my life."

"I learned about what he ate, what kinds of things he did in his spare time, what annoyed him, what he loved, what he didn’t love," Worthy explained. "It was hard because there was only so much video footage of him so I only had this outline of Nick and had to color in the rest."

Godejohn is autistic and Worthy was laser-focused on creating an "authentic" depiction of the real-life man. "I spent a lot of time at the Long Beach Autistic Center, watched countless documentaries and read tons of literature. "I didn’t want to act; I wanted to be Nick," he said.

The first two episodes of "The Act" drop on Hulu on March 20.