The true story behind The Good Nurse: Here's what really happened

Warning: This article contains spoilers for The Good Nurse.

When you get sick, you go to a hospital to get better. It's that simple: Patients inherently trust that the doctors and nurses there will help them. But Netflix's The Good Nurse reveals how one nurse twisted that undying faith in the healthcare profession into something horrifying, becoming one of America's most prolific serial killers in the process. The story itself is deeply unsettling because of how Charlie Cullen (played by Eddie Redmayne) was able to get away with it for so long, despite getting caught over and over again by the hospitals who employed him, until one brave nurse, Amy Loughren (Jessica Chastain), finally brought him to justice.

But what makes it even more shocking is that it actually happened in real life. Director Tobias Lindholm's movie is an adaptation of Charles Graeber's 2013 book The Good Nurse: A True Story of Medicine, Madness, and Murder, an excellently researched and detailed account of the true story of Loughren and Cullen.

Below, EW breaks down the biggest moments from the film and the truth behind them — but be warned, your faith in the healthcare system may plummet after reading just how real this story actually is.

Are Amy Loughren and Charlie Cullen real people?

They absolutely are. The Good Nurse is told from the perspective of Loughren, a single mother working night shifts as a nurse while struggling with a life-threatening heart condition. Already stretched to her physical and emotional limits by her demanding job, she soon becomes suspicious of her new coworker and friend Cullen after a series of mysterious patient deaths spark an investigation. Amy ultimately risks her life and the safety of her children to uncover the chilling truth about Charlie — that he'd been injecting saline bags with deadly levels of drugs (mostly insulin or the heart medication digoxin) to kill patients via overdoses.

In real life, Cullen began his nursing career in 1987 at New Jersey's Saint Barnabas Medical Center, and police claim that it was only a year before he committed his first murder there. He continued killing patients until he left the hospital four years later when officials started investigating contaminated IV bags. But he was never charged with any crimes. That's how he was able to get another nursing job at Warren Hospital a month later and continued killing patients.

Cullen went on a murder spree for over a decade and a half after that, working and killing at many different hospitals. Each time his actions were investigated and uncovered, the hospital's lawyers and administrators decided to fire him but not report the crimes to police to avoid any wrongful-death lawsuits. At least five different hospitals knew what Cullen was doing and did nothing to stop him. Their decision to cover up the truth is what allowed Cullen to continue his career as a nurse — and murderer. It wasn't until he started working at Loughren's hospital, Somerset Medical Center, and became close with her that everything unraveled for him, because she refused to ignore what so many others had before.

"Watching the movie gave me permission to be proud of myself," Loughren told PEOPLE. "I showed up as a mom. I showed up as a nurse. I showed up as a friend. The only reason Charlie is not still murdering is because of my friendship with him."

What about the identity of the victims?

While Loughren and Cullen's real names and story were used in the movie along with the real names of the detectives (played by Noah Emmerich and Nnamdi Asomugha), all of the victims and their families are fictionalized. Screenwriter Krysty Wilson-Cairns told Vanity Fair she changed all the names so as not to "revictimize them. We weren't in those rooms. I didn't meet the victims' families to really understand who these people were. So frankly, I would feel a bit dirty [using their identities]. And most people could not give consent because they were dead. Or sometimes the families didn't know. In the case of a lot of Charlie's victims, the families still don't know."

However, all the other facts of the case, including how detectives had a body disinterred for an autopsy, are true.

How did Loughren catch Cullen?

Just as it happens in the movie, Loughren started to become suspicious that Cullen may be behind the mysterious deaths happening to her patients. It only took her six months to stop a 16-year killing spree. She eventually became a confidential informant to help police gain enough evidence to arrest Cullen in 2003. That scene where she wears a wire and confronts him about his crimes in the diner? That really happened. And just like in the movie, after he was apprehended by authorities, she appealed to Cullen's humanity and used empathy to get him to ultimately confess to murder when the evidence alone wasn't enough to convict him.

Loughren's identity wasn't revealed until Graeber's book came out in 2014, however — she truly was a silent hero that brought down a serial killer. Thanks to her efforts, he is currently serving 11 consecutive life sentences and faces another six life sentences.

Did he really murder that many people?

During the film's climactic third act scene, Loughren gets him to confess to 29 murders — and he eventually told investigators that number is actually 40. But it's even worse than that. Graeber, the author of the book, discovered through his own investigation that Cullen told detectives he "dosed" three to four people a week and didn't follow up to find out what happened to them. Doing the math over 16 years, experts now believe Cullen is responsible for over 400 deaths, making him one of the worst serial killers in history. He eventually became known as the "Angel of Death."

In 2013, Cullen was interviewed on 60 Minutes and said that while he knew what he was doing was wrong, he never would have stopped killing if he hadn't been caught. "I thought that people weren't suffering anymore," he said during the interview. "So in a sense, I thought I was helping."

But he never revealed why he started killing patients in the first place. "There is no justification," he said. "The only thing I can say is that I felt overwhelmed at the time. It felt like I needed to do something, and I did. And that's not an answer to anything."

Did Loughren really suffer from a life-threatening heart condition?

Catching a serial killer while working a full-time job as a night-duty nurse (and also raising kids as a single mother) is hard enough. But Loughren was also risking her life every day by not getting the heart transplant she desperately needed — because she was trying to wait until her health insurance kicked in first. Loughren really was suffering from a life-threatening heart condition at the time, which is how she became so close to Cullen; he was helping take care of her as her health worsened.

Screenwriter Wilson-Cairns and Chastain both met the real Loughren to make the film's portrayal of her authentic, especially when it came to her heart condition. "I asked her about her heart condition because she needed a heart transplant during this time," Chastain told EW. "And that to me was the thing that really helped me in playing the character is understanding what it meant when I went into Afib [a.k.a. atrial fibrillation], what it meant when my heart started beating at a certain level, what it would do to my breath, what it would do to the temperature of my skin, if I'd get clammy — all of these things were very important."

Where is Cullen now?

Still behind bars — for a long, long time. Cullen is currently serving one of his many life sentences at New Jersey State Prison, and the earliest possible parole date would be June 10, 2388, according to the Department of Corrections.

The Good Nurse is now playing in select theaters and begins streaming Oct. 26 on Netflix.

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