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After a nightmare, the coat on the chair can still look like a person. You recognize the room, yet the fear takes longer to leave. Horror films exploit that uneasy return to consciousness. A character wakes, the audience relaxes, and then something moves where it shouldn’t.

The question underneath is old: is a frightening night something the mind produces, or something that visits? Science has answers for a great deal of it. Many spiritual traditions have answers of their own, and people explore them in different ways: by keeping a dream journal, talking with a friend or a priest, or speaking with a reader on Nebula. Those interpretations are matters of belief.

Sleep gives filmmakers several ways to make a private fear appear to act upon the world. A dream can bring a character’s suppressed feelings into a conversation they would otherwise avoid. It can also give a monster access to someone who was safe a moment earlier. The uncertainty about what is happening matters, but a film can settle that question and still leave its characters in terrible danger.

The feeling of a presence

Some frightening experiences at the edge of sleep have a physiological explanation. Sleep paralysis occurs when the muscle atonia associated with REM sleep persists into conscious awareness. A person can be aware of their surroundings and unable to move. Hallucinations may accompany the paralysis, including a sensed presence or the impression of pressure on the chest. The experience can be terrifying even when someone understands what is happening.

Henry Fuseli's The Nightmare, painted in 1781, supplies a memorable image of a bedroom invaded. A woman lies across a bed with an incubus crouched on her chest; a horse peers through the curtains. The painting gives a disturbing bodily sensation the shape of an encounter. Its sleeper shares her room with something that can look at her while she cannot look back.

That arrangement suits horror cinema. A sleeping character cannot inspect the space around them or respond to what the camera reveals. The audience can see an intruder approach and wait for a victim to notice.

When waking offers no escape

In Wes Craven’s A Nightmare on Elm Street (1984), Nancy Thompson falls asleep in the bath while Freddy Krueger’s bladed glove rises from the water between her legs. We see the hand before Nancy does. The shot gives us time to recognize how exposed she is.

Her mother’s interruption briefly disperses the threat. She warns Nancy that she could drown if she falls asleep in the tub, an ordinary piece of parental concern that becomes horribly appropriate. When Nancy is pulled underwater, the shallow bath opens into an impossible depth. Craven turns a familiar room into a place where Nancy cannot trust even the distance between her body and the floor.

The scene needs little uncertainty about whether the attacker is real. Its immediate fear comes from Nancy’s inability to remain alert. Her mother understands that sleep can be dangerous in a bath, but she cannot imagine the danger her daughter faces. Nancy’s home offers adult supervision without effective protection.

David Lynch moves the disturbance into daylight in Mulholland Drive (2001). At Winkie’s diner, Dan tells his companion, Herb, about a recurring dream. In it, he is frightened by the presence of someone behind the building. He has come to the diner hoping to get rid of the feeling.

Lynch gives the audience that account before taking the men outside. By the time they approach the corner behind Winkie’s, Dan has supplied enough information for us to dread what they will find. A figure comes into view, and Dan collapses.

The scene’s force depends on the time spent anticipating the encounter. Herb’s willingness to investigate suggests that a walk around the building might settle Dan’s fear. Instead, the walk brings them to the image he has described. The dream has begun to dictate their movements through an otherwise ordinary place.

Craven and Lynch give waking different consequences. Nancy struggles to escape an attacker who reaches her through sleep. Dan is already awake when he follows the course of his dream. Neither scene needs the audience to remain evenly divided between a medical explanation and a ghost story. Both make the promise of returning to normal life unreliable.

The family inside the nightmare

In Hereditary (2018), Ari Aster uses a dream to bring a mother’s concealed feelings into her son’s bedroom. Annie tells Peter that she never wanted to be his mother. She insists that she loves him, but he brings up her attempt to kill him. His accusation makes it impossible for her reassurance to settle the conversation.

The scene becomes more disturbing when Peter is drenched in liquid and fire erupts. It recalls an earlier sleepwalking incident Annie describes: she woke to find that she had covered herself and her children in paint thinner. Peter’s accusation connects Annie’s admission about motherhood to that violence. Her son has reason to fear the person who is supposed to protect him, and the dream forces her to hear it.

Aster’s discussion of the scene in a 2018 Reddit AMA makes its conflicting motives particularly clear. He describes Annie’s sleepwalking violence as suppressed resistance to her mother's plans for the family, while also allowing a reading rooted in Annie’s hostility toward a maternal role she never wanted.

Those possibilities converge in the same frightening action. A mother trying to save her children by setting them alight remains a threat to them. A supernatural explanation cannot make that relationship safe. The film eventually confirms the cult’s assault on the family, but the dream has already exposed a source of fear within its closest bond.

Jennifer Kent’s The Babadook (2014) approaches that bond through exhaustion. Samuel’s fear repeatedly interrupts his mother Amelia’s rest. His need for protection keeps her awake, and her growing inability to cope makes the home more frightening for him. Bedtime becomes a recurring conflict between two people who depend on each other.

The sinister book Amelia reads to Samuel turns a familiar act of care into another disturbance. Reading together should help him settle. Instead, Mister Babadook gives his fear an image and a name that Amelia then struggles to keep out of the house. The more threatening she becomes, the harder it is to separate his fear of the creature from his fear of her.

The film connects that strain to Amelia’s grief over her husband, who died while driving her to the hospital to give birth to Samuel. Her son’s birthday marks both his arrival and her loss. His ordinary needs continually demand attention from a mother who has never found a way to live comfortably with that history.

Calling the Babadook either a monster or grief misses how these elements work together. Asked whether the creature was real or in Amelia’s head, Kent answered affirmatively to both possibilities. The creature’s place in the story allows the film to give grief a physical presence without resolving it into a simple diagnosis.

The ending makes that relationship tangible. Amelia takes a bowl of worms to the Babadook in the basement, then returns to Samuel. The creature remains part of the house even as mother and son begin to live more comfortably together. Caring for Samuel has become possible alongside acknowledging something Amelia previously could not face.

Dreams and hauntings meet in these films because both can make a home feel occupied by fears its residents cannot control. Sleep helps the films move between a character’s experience and an apparent threat in the room. Sometimes waking interrupts that movement; sometimes it gives the threat another opportunity.

Recognizing what is happening offers no automatic release. Dan’s account prepares him for the figure behind Winkie’s without making the encounter bearable. Annie’s nightmare exposes a danger that cannot be confined to the dream. Nancy can learn Freddy’s history and devise ways to fight him, but her body’s need for sleep keeps giving him a way back in.