A new true crime drama is out on Netflix — and no, I’m not talking about The Watcher or Monster: The Jeffrey Dahmer Story.

The Good Nurse is a gripping film that follows Amy Loughren (Jessica Chastain), a nurse who befriends fellow nurse Charles Cullen (Eddie Redmayne) when he starts on her unit. Little does Loughren know, Cullen is a murderer behind the deaths of multiple patients.

The Good Nurse is based on journalist Charles Graeber’s 2013 book of the same name. Let’s run through some of the major takeaways about the real Cullen and Loughren.

Who is Charles Cullen?

Charles Cullen pleaded guilty to killing 29 people when he worked at hospitals in New Jersey and Pennsylvania, according to NJ.com. But the true number of victims may be much higher.

Graeber, the author of the book on which the movie is based, told CBS News in 2013 that he would “be very surprised, as would pretty much everyone I’ve spoken to with any knowledge of this case, if it was not in the hundreds, multiple hundreds.”

“We’ll never know how many people Charlie Cullen ultimately killed,” Graeber told NPR.

How did Cullen kill hospital patients?

Cullen killed victims with medications such as the heart drug digoxin, according to CBS News.

Victims ranged in age and health, with some “ready to be discharged when Cullen injected them with drugs that would kill them,” according to the news site.

Jessica Chastain as Amy Loughren in The Good Nurse.
JoJo Whilden/Netflix

Who is Amy Loughren?

Loughren worked with Cullen at New Jersey’s Somerset Medical Center and helped police investigate him, according to NJ.com.

She was a single mother working night shifts when police told her he was a serial killer, according to Glamour. Cullen had been Loughren’s close friend and had helped her conceal a heart condition at work. The news shocked her, according to the magazine.

What parts of the The Good Nurse are fictionalized?

The movie does fictionalize aspects and change details, according to the Los Angeles Times. Still, Graeber told the newspaper he “felt that it was accurate in its essence.”

“[The real story here is] about institutions, the banality of evil and individuals and the choices they make,” Graeber said. “I feel that this film nails that.”

None of the deaths in the movie are based on real victims, director Tobias Lindholm told the Times. Still, “the methodology of the murders” remains the same, he said.

Why did Cullen do it?

CBS News correspondent Steve Kroft asked Cullen about his motivation in 2013. “I thought that people weren’t suffering anymore,” Cullen said. “So, in a sense, I thought I was helping.”

After Kroft pointed out that Cullen murdered people “who were not near death, and not suffering that much,” Cullen said “there is no justification” and “the only thing I can say is that I felt overwhelmed at the time.”

Where is Cullen now?

Cullen is serving multiple life terms at the New Jersey State Prison in Trenton. According to NJ.com, he’s currently 62.