Photo via Apple TV

In the cold, blank grey of a high-security cell, Jurek Walter (Stephen Graham) sits preternaturally still, legs crossed, hands in his lap, whispering into the sink beside him. His voice emerges from the pipes into another cell, entreating its resident to suicide: “There’s only one way to stop the pain,” he coaxes. Eventually his victim runs, full tilt, into the opposite wall, caving in his own head. It’s an opening that seems almost to shout: “You’re going to want to watch this!” Unfortunately, Nocturne oversells itself.

We return in the next scene to Riverside Psychiatric Hospital, but in the intervening six months the show’s menace and drive have leached away. Nurse Karl (Rory Culkin), with his gullible wide blue eyes, has a way with psychos and madmen. In a heavy-handed bit of characterisation, we are shown in quick succession how he helps patients no one else can reach; he treats them like human beings when no one else does, as though he can cure them with kindness.…