Spoilers ahead for the latest episode of Castle Rock, “The Queen.“

For decades, mental illness has been a scapegoat for the horror genre. If you needed a surprise explanation for why a character is violent, just throw in the word “crazy” and name some medical condition. But Hulu’s newest series, Castle Rock, which presents an original story set in the universe of Stephen King’s vast mythos, changes that by introducing a character by the name of Ruth Deaver, played by Sissy Spacek. We don’t know much about her, besides the fact that she is the adoptive mother of our main character, Henry, and she suffers from a form of dementia.

This week’s episode centers on Ruth being haunted by repressed memories of her marriage with her deceased husband, all while trying to remember where she put a box of bullets. It’s a simple story told beautifully that has been compared to “The Constant,” from Lost, for its self-contained story that still advances the overarching plot. More than that, the episode manages to put the viewers in the shoes of a woman with dementia to portray what it’s like to truly be lost in your memories.

What makes Castle Rock stand out is that the character suffering from mental illness is not treated as a surprise, or as a threat, but as a human being. The use of “crazy” people in horror cinema can be traced to one of the earliest uses of the plot twist in cinema, the German Expressionist film The Cabinet of Doctor Caligari from 1920, which uses exaggerated set designs to represent the mind as it descends into madness. The film focuses on an evil doctor controlling a somnambulist, or sleepwalking man, to attack people including the main character, who tries to stop him. In a twist ending, the film reveals that the main character was an unreliable narrator, as he actually was an asylum inmate.

After Caligari, those with mental illness became the “other” of horror films, used routinely as a twist to explain why someone would be capable of doing horrible things while blaming it on a proxy. This didn’t improve once Alfred Hitchcock decided to adapt Robert Bloch’s book Psycho into his seminal film of the same name. The film again uses the plot twist to reveal that Norman Bates’ violence is a result of having dissociative identity disorder, which is also used in films like Shutter Island and Split.

Castle Rock treats Ruth as a full character, not just as a person with dementia. Because she is neither protagonist nor villain, the show doesn’t rely on her condition to move the plot forward at the expense of her characterization. We spend much of Episode 7, “The Queen”, following Ruth as she loses herself in memory after memory, using chess pieces as a coping mechanism to find her way back to the present. The writer of the episode, and co-creator of the show, Sam Shaw, describes the difficulty in making dementia visually accessible for the audience:

“One choice really early on was that it would be interesting to think of a visual metaphor for dementia that didn’t just suggest a kind of loss or diminishment of her experience, but sort of suggest that she lives in this memory palace where all of her memories are alive and filling up the house.”

We see Ruth going from memory to memory, finding it harder to get back to the present, the audience not aware if her memories can be fully trusted.

While most horror films use the trope of the unreliable narrator for superficial shock value in a third act plot twist, there are films that use mental illness to color every scene with fear that feels real. From Natalie Portman’s descent into paranoia as a ballerina in Black Swan, to Tim Robbins’ PTSD-stricken veteran in Jacob’s Ladder, hallucinations and an unreliable narrator can keep the viewer on guard and afraid of what’s coming next. Shaw wanted to use the unreliability of Ruth’s memories to put the audience in her shoes, by having the structure of the episode as chaotic as her mind:

“As the episode goes on, her memories start to collapse on each other. I felt really strenuously that there are no rules to dementia, and presenting this episode with clear and organized rules would be dishonest. Dementia isn’t like an IKEA crib, it doesn’t come with instructions. Even Ruth’s coping mechanism fails her at a certain point.”

This is not to say that mental illness doesn’t belong in the horror genre. As seen in Steven Soderbergh’s Unsane, there are few things that are scarier than the feeling that you can no longer trust your brain, that something inside of you is against you. What it means is that mental illness should not be reduced to a simple trope. Recently, M. Night Shyamalan’s Split was critically acclaimed as a return to form for the horror director, despite the film sensationalizing mental illness as it focuses on a man named Kevin who is suffering from dissociative identity disorder. We find out (spoiler!) that his illness also includes a personality that is a murderous supervillain. The film goes so far as to have a character be a psychologist with the controversial theory that DID gives sufferers extraordinary abilities because they use more of their brains, all so Shyamalan could tie the film with another one of his projects.

In Episode 6 of Castle Rock, the show came close to arriving at the same conclusion, as we see Ruth telling her grandson Wendell that she doesn’t believe she’s losing her memories, but she’s becoming unstuck in time. Some comments on Twitter took this to mean that she can somewhat travel in time, because nothing is as it seems in Castle Rock. Shaw didn’t want to spell out an answer to the audience, but thinks it’s all there:

“There’s a scene early in the episode at the neurologist’s office, where we show the name of our monster, which is Alzheimer’s. We see this in the reactions from Scott Glenn’s character, Alan Pangborn. Those who’ve read Stephen King’s novels know he’s faced some otherworldly forces before, but this scene shows him completely powerless in the face of this monster, unable to help Ruth.”

The conversation around representation of mental illness is picking up, with recent films like The Babadook and Hereditary making some progress in showing the horrors of mental illness without making monsters out of the characters suffering from it. But if we want to stop the damage done by films like Psycho, then Castle Rock is a step forward, by not using mental illness as a plot device, but by putting the audience in the shoes of someone suffering from it.

For more on Castle Rock, be sure to keep up with our weekly Stephen King Easter Eggs guide.