Rory Culkin plays Karl in Apple TV's Nocturne, and the role puts him inside the series’ central pressure point. Karl is a new nurse at Riverside Psychiatric Hospital, where Jurek Walter starts building a tenuous bond with him.
The 10-episode series reached critics with seven episodes screened for review, giving the early read enough material to place Karl near the center of the show’s serial-killer story. That setup gives Apple TV a thriller built around institutional routine, patient access, and manipulation rather than a simple cat-and-mouse chase.
Riverside Psychiatric Hospital
Nocturne begins at Riverside Psychiatric Hospital in rural Pennsylvania, where the opening movement of the series puts the hospital itself under strain. Rory Culkin’s Karl is described as quiet and reserved, which makes him a natural fit for a job that depends on discretion, but it also leaves him exposed to a patient who knows how to work people.
Stephen Graham plays Jurek Walter, and the character’s attention shifts the story from procedure to persuasion. The review places Karl in the path of that manipulation early, which means the series is not just using the hospital as atmosphere; it is using it as the place where trust becomes a liability.
Jurek Walter and Karl
Jurek Walter’s bond with Karl is called tenuous, and that word does real work here. It suggests a relationship built on small openings rather than open confrontation, the kind of setup that lets a thriller squeeze more out of silence, routine, and short exchanges between nurse and patient.
The review also says Karl constantly bypasses Riverside protocol without alerting security while trying to please Walter. That friction gives the role its edge: the nurse is not simply reacting to danger, he is making choices that deepen it, which turns a hospital worker into the story’s most vulnerable point of entry.
Seven episodes in view
Seven screened episodes are enough to show where Nocturne is headed: the series is built to keep Karl’s judgment under pressure while Walter’s manipulation widens. With Liev Schreiber in the cast and the story based on Lars Kepler’s Lazarus and The Sandman, the show is clearly aiming for a long fuse rather than a quick reveal.
Rory Culkin’s Karl is the reason this matters now. He is not written as a flashy lead; he is the quiet professional whose need to please the wrong man can move the whole story, and that is the part of Nocturne that looks most worth watching.
