Amy Loughren (Chastain) is a nurse at an average New Jersey hospital, trying to balance being a single mother with her high-stress job. This gets even harder when she’s diagnosed with a cardiac condition that could kill her if she doesn’t get a heart transplant in time. She keeps the diagnosis from her bosses, staying on at work because she hasn’t been there long enough to get the health insurance needed to deal with it. The heart issue adds a ticking time bomb aspect to “The Good Nurse” in that if the tension of what’s about to happen causes too high a heart rate in Amy, she could die.

She thinks the opposite is going to happen when she meets the kindly Charles Cullen (Redmayne), a new nurse who befriends Amy and offers to help her with her patients, and even with taking care of her children. At first, Charles seems like a lifesaver, a colleague who knows Amy’s secret, and wants to be there to help. Amy has no idea that the hospital, led by an icy Kim Dickens as its callous representative, has alerted the local authorities to a concerning situation involving the inexplicable death of one of Amy’s patients. With little warning, a woman coded, and an abnormal amount of insulin was found in her system. She was clearly double dosed, and the hospital really only let the cops know so they could be prepared for any legal liability. The investigating officers, played by Noah Emmerich and Nnamdi Asomugha, start digging a little deeper and find a disturbing work history for Mr. Cullen involving nine other hospitals, all of which he left with rumors swirling. And then another one of Amy’s patients dies

Would Charles Cullen, who it is confirmed killed at least 29 people—though it’s suspected the total may have been in the hundreds—have ever been caught without the courage of someone within the system? The truth is that the lawsuit-terrified operations that hired and fired Cullen didn’t come close to performing their moral duties, shuffling a serial killer off to his next victim. And as long as that kind of business-over-ethics principle was in place, Cullen could have continued. Lindholm was clearly drawn to the hero arc of this true story, the one person who broke the pattern by helping authorities, even though she had so much to risk to do so.

And that’s about where the development of these characters ended. We learn so little about Amy and Charles beyond the facts of the case. Amy is a mother with a heart condition. That’s pretty much the extent of it. Yes, there’s something to be said for a thriller that focuses so intently on its true crime story that it feels like it almost traps you in it, but this movie doesn’t do that either because it’s too languid. It’s a two-hour version of a remarkably thin screenplay, one that often mistakes slow for subtle. And maybe it’s a Netflix thing where so many new shows and movies have to look like “Ozark,” but I was begging someone to turn on a light once or twice. Some filmmakers mistake low lighting and speaking quietly for important drama, and it’s just silly. But it speaks to how performative too much of “The Good Nurse” is in the end.