A thousand-yard stare into the dark soul of the US healthcare model, Tobias Lindholm’s The Good Nurse portrays its real-life serial killer subject as a symptom of a greater, prosaic evil. Eschewing sensationalism to focus on the ruthless monetisation of mortality — with a light touch on the real Charlie Cullen and a grim insistence on the system that enabled him — the film makes a nihilistic waking nightmare of its source material in a fitting change from the true crime genre.

Our guide into this cesspit is Amy Loughren (played by Jessica Chastain), a weary single mother and nurse facing her own healthcare nightmare in the form of fatal cardiomyopathy. In dire need of a heart transplant, Amy must lie about her condition to keep the exhausting nighttime shifts at work until her health insurance kicks in — a real-life predicament that mirrors the hopeless cycle in which so many of her patients are trapped. Tending to her charges with the compassion denied by her employer and the healthcare sector in general, Amy’s burden is eased somewhat by the arrival of kind, sensitive new nurse Charlie (Eddie Redmayne), a rare example of a caring human in the bleak hospital landscape.

With Redmayne making the most of his waiflike, sexless demeanour, Charlie proves a sweet-natured and unthreatening support to Amy, bringing the patience and empathy so strongly expected of a care provider (and less so of a rugged American man). He bonds with Amy's young daughters, referring to the heartless ex who keeps him from his own children, and becomes work bestie to our heroine, offering no cheapening suggestion of romance but a rare bond over shared compassion in a deliberately cold and clinical environment. As Charlie steps up in Amy’s life outside work, helping to handle childcare and errands, he quietly illustrates the spiralling demands on working people, and the hopeless gap in their provision; Amy shares her struggles with no one but the viewer in earlier scenes, and for a brief moment it seems she’s found a remedy to the waking nightmare of her workplace.

The natural camaraderie shows Amy’s discovery to be all the more wretched and disillusioning. Tobias Lindholm and his stars approach the revelation with a slow, bleak tension, punctuated by emotionally fraught but unglamorous offscreen deaths, or the contrasting drama of a patient “coding” or going into cardiac arrest. One might call it clinical, but the crests and troughs of a hospital drama soon settle into a depressing numbness, punctured by the procedural stodge of detectives Baldwin (Nnamdi Asomugha) and Braun (Noah Emmerich). As the cops plough through the growing pile of unexplained deaths at Charlie's hospital — with all the benevolent ineptitude of Ice T on SVU but none of the wisecracks — some viewers may long for a return to the compelling dynamic between the leads.

In the final act, Redmayne and Chastain’s respective ‘snaps’ convey the suffocating impact of the hospital: Amy’s humanity leads her to messianic levels of both strength and suffering, but it’s the sociopathic contours of Charlie’s mind that liven up the end of his arc at last. Viewers expecting Lecter-level pantomime villainry are likely to be disappointed by The Good Nurse, which flatly resists a strong emotional engagement with the psyche of the serial killer estimated to be responsible for the deaths of up to 400 people at US hospitals in the 80s and 90s.

Redmayne’s performance, and the tightly scripted film, communicate the enduring and painful mystery of why he did it in the first place. Quiet, watchful, often insipid, his Cullen switches in a terrifyingly plausible fashion from care and attentiveness, to dead-eyed inscrutability, eventually lighting up at the prospect of another victim. This cool and detached film might offers a clear-eyed perspective on America’s exploitative healthcare system, but leaves its real-life subject an appropriately grisly mystery.