Before the stage show ends and Dorothy sings "Blue Star," they drive back together to the Deep River Apartments to surreptitiously trespass into her unoccupied apartment, but Sandy is worried that his plan is "crazy and dangerous." To help notify when Dorothy returns, Sandy remains with the car, planning to honk four times when she is "on her way up." Sandy asserts the definitive dichotomy in the film when she cannot distinguish whether Jeffrey is a "detective or a pervert" - he's probably a combination of both ends of the spectrum:

Sandy: I don't know if you're a detective or a pervert.
Jeffrey: Well, that's for me to know and you to find out.

Jeffrey enters her still, dark vacant apartment with the stolen key, searching for evidence and clues hidden there. In one of the rooms, he sees a small pointed children's party hat decorated with musical notes and a propeller on top [identified by some reviewers as one of the many film references to The Wizard of Oz (1939)]. Interrupting his search to urinate (because of the "Heineken") in her bathroom cluttered with perfume bottles and cosmetics next to a mirror, the sounds of Sandy's four coded honk blasts are drowned out by the flush of the toilet and he doesn't hear the warning when Dorothy suddenly appears. When she is heard entering the apartment with her key, Jeffrey hides in the apartment behind a wardrobe closet door and peers through the venetian blind-type slats to see her enter.

In one of two memorable and shocking scenes in the film, Jeffrey hides in the closet of Dorothy's apartment and voyeuristically watches her as she disrobes to a black bra, black panties, and red high-heeled shoes [a connection to Dorothy's magical ruby slippers in The Wizard of Oz]. She approaches toward the closet where he hides but the phone rings and she turns away to answer it. He overhears her cryptic and confusing phone conversation (a message later interpreted as being from a sadistic, criminal kidnapper named Frank who holds her husband Don and son little Donny hostage while making her his sexual slave):

Hello. Yes sir. Frank. Frank, let me talk to him. Please Frank, sir. I like to sing Blue Velvet. Don? Don? It's all right. Don't worry. Don?? Don? Can you hear me? Is little Donny all right? Is he there with you? Don? You mean Meadow Lane? Frank, Frank, what's the matter with him? In an hour. I'll be sweet. Mommy loves you. OK, Frank, sir.

Then on her hands and knees on the floor, she looks at a framed photograph that is kept under the sofa, and then hides it in its place. She crawls across the living room floor, removes her black wig to reveal her own hair underneath, and then goes down the hallway to the bathroom at the end of the hall. All the while, Jeffrey watches her through the louvered slats, casting a line of light across his eyes. There in the bathroom, she removes her shoes, bra and panties, and then returns to the living room wrapped in a bright red towel. She reaches for a blue velvet robe from the closet, as he ducks and hides. Then she returns to the sofa for a few moments.

Jeffrey only hears noises as she slowly walks out of view into the kitchen. He hears a drawer open as she reaches for a large knife. She flings open the closet door and he is caught and threatened at knife-point into intimidation and forced to get on his knees:

Dorothy (screaming): Get out of there. Get out! Put your hands up on your head. Do it! Get on your knees. Do it! What are you doing? Who are you? What's your name? What's your name?
Jeffrey: Jeffrey.
Dorothy: Jeffrey what?
Jeffrey: Jeffrey nothing.

She cuts his face with the knife blade and then finds out that his name is Jeffrey Beaumont and that he only wanted to see her. Knowing that he looks familiar, she learns that he was the exterminator. Dorothy asks: "Do you sneak into girls' apartments to see them get undressed?" Feeling guilty, he responds: "Never before this."

Turning the tables on him, she makes him her voyeuristic prey, forcing him to undress in front of her, all the way down to his boxer shorts and socks. The loud, tearing, unzipping sound of his zipper is emphasized. Commanding him to stand and submit to her advances, she pulls down his boxer shorts to the floor, but doesn't allow him the pleasure of watching:

Get undressed. I want to see you...I want to see you. Get undressed...Come closer, closer. What do you want? Don't move. Don't look at me.

While kneeling in front of him with a knife poised in a threatening manner, Dorothy begins touching, fondling, and kissing (and fellating?) him, forcing him to remain motionless. She asks: "Do you like that?" and then asks a question combining domination, pain, power, pleasure, and humiliation: "Don't touch me or I'll kill you? Do you like talk like that?" [Her questions and behavior foreshadow the behavior of her own perverted sex partner Frank.] Responding with nervous ecstasy, arousal, but defenseless fear, he is led to the couch to lie down where she straddles him and kisses him.

Three loud knocks at the door frighten Dorothy. Frantically fearing the man's arrival and with the knife gleaming above Jeffrey, she tells him to head back into the closet:

Shut up. Don't say anything. Go hide in the closet. Don't say anything or he'll kill you. I mean it.

Totally nude except for his black socks, Jeffrey rushes to obey - picking up his clothes and then returning to the closet, hiding stark naked.

Maybe the meanest, most repulsive, vilest villain in film history - the memorable deviant, fiendish, evil sadist Frank Booth (Dennis Hopper) wearing a black leather jacket enters the living room. The following scene - a disturbing, cruel, sadomasochistic, kinky scene, begins by Frank's primal display of annoyance, angrily cursing at her. Demanding and condescending to her, he establishes an abusive master/victim relationship over Dorothy as she accommodates his depraved preferences. The 'dark' scene is intercut with a frightened Jeffrey surreptitiously viewing the shadowy, broken images between the slats of the distasteful ordeal from his hiding place in the closet:

Dorothy: Hello baby.
Frank: (reprimanding) Shut up. It's Daddy you s--t-head. Where's my bourbon?
(She goes into the kitchen and gets Frank his drink, handing it to him.)
Can't you f--kin' remember anything? (Dorothy turns out the main light in the living room and lights one small candle.) Now it's dark. (Wearing her blue velvet robe, Dorothy sits on a chair in the middle of the living room. Frank sits down on the sofa.) Spread your legs. Wider. Show it to me. (She slowly opens her legs wider and adjusts her robe, while Frank stares at her crotch and drinks his bourbon.) Don't you f--kin' look at me!

Traumatized, Jeffrey watches Dorothy being tormented as Frank's sexual slave/whore. He repeatedly demands that she look away from him - denying her the sight of his 'dark' nature. [In a symbolic sense, Jeffrey - as a child - illicitly spies on the scene of seduction that his parents are having sexual intercourse - Dorothy ("Mommy") and Frank ("Daddy" or "Baby"), causing irreversible psychic damage.] The abusive scene is heightened when the black-dressed Frank reaches for a portable, plastic gas-inhaling mechanism and mask on his belt. [Sexual activity normally commences with heavy breathing.] While he places the insect-like mask over his mouth and nose, he snorts and inhales (helium?) gas to heighten his sexual excitement, exhibiting infantile-regressive, animalistic/reproductive, and compulsive-addictive behavior, debasing her as both a prostitute, mother figure, or copulatory partner in the natural world:

Frank: Mommy. (He moves toward her, kneeling in front of her.) Mommy. Mommy. Mommy.
Dorothy: Mommy loves you.
Frank: Baby wants to f--k. Get ready to f--k. You f--ker's f--ker. You f--ker. (He slugs her in the face.) Don't you f--kin' look at me!

After another gasp of gas, Frank begs and whines menacingly:

Baby wants blue velvet.

Dorothy stuffs part of her blue robe into his mouth to satisfy his obsession with textured fabrics. As he begins to feel her breasts, he sucks, chews, and bites the velvet cloth. Then he seizes her and throws her down to the floor, spewing vulgar words. Frank removes a pair of scissors, menacingly snipping with them in mid-air above her face and body:

Don't f--kin' look at me. Don't f--kin' look at me. Don't you look at me. Daddy's coming. (He stuffs the end of her blue robe belt into her mouth and the other end into his own mouth.) Daddy's coming home. Don't you f--kin' look at me. Daddy's coming home...

And then after forcefully touching her genitals, he mounts her and starts humping her with his unbuckled pants still on. He moves frenziedly faster and faster until climaxing in a brief and brutal f--k. After getting off of her, he slugs her again in the face, hideously threatening her again: "Don't you f--kin' look at me." He stands and blows out the candle which burns in Dorothy's wall lantern: "Now it's dark." Standing astride her on the floor before he leaves, he warns: "Stay alive baby. Do it for Van Gogh." [Frank has sexually blackmailed her, threatening her with further torture of her kidnapped husband, the owner of the severed - or castrated ear.] Then he marches out of the apartment, shutting the door behind him and leaving her crumpled on the floor.

Stunned by the repellent scene he has witnessed (something profane that really needs exterminating), Jeffrey emerges from the closet and goes to console her. He touches her head - surprising her and causing her to flinch. She mistakes him for Don - the name of her missing, kidnapped husband. He helps her to the sofa where she turns away from him toward the wall, pushing away a cover he puts over her. In another role reversal, he comforts her as a victim of aggressive, ugly and vile sexual behavior. She implores him to violently brutalize her as an active and willing participant:

Dorothy: ...What do you want?
Jeffrey: Nothing. Are you all right?
Dorothy: Yeah. I'm all right...
Jeffrey: I'll go then.
Dorothy: Don? Oh Don.
Jeffrey: No.
Dorothy: Oh Don. Hold me. Hold me. I'm scared. I'm scared. I'm scared. (She clinches him tightly to herself.)
Jeffrey (whispering): It's OK. It's OK.
Dorothy: (She touches his face.) Do you like me? Do you like me?
Jeffrey: Yes. (Sensually submissive, she lies limp in his arms in surrender, her red-lipsticked lips brightly highlighted in close-up.)
Dorothy: Do you like the way I feel?
Jeffrey (whispering): Yes.
Dorothy: (She opens her robe to reveal her left breast, tempting him.) See my breast? You can feel it. My nipple. Still hard. You can touch it. You can feel it. (Jeffrey responds, touching her.) Do you like the way I feel?
Jeffrey (whispering): Yes.
Dorothy: Feel me. Hit me. (She bangs her fist into the wall)
Jeffrey: No. Dorothy no. Stop it. (She rolls out of his arms.)
Dorothy (pleads): Hit me! Hit me! Hit me!

Alarmed by her requests, he refuses, and she responds by moving away from him and going down the hallway to the bathroom. Succumbing to his sense of morality, Jeffrey dresses to leave and announces: "I'm leaving now," while noticing a swatch of blue cloth ripped out of the hem of Dorothy's robe and hearing her say softly: "Don't. Don't. Love me." Just before leaving while alone in the living room, he sneaks a look at the framed photograph under the sofa (a picture of a man and a small child in his arms wearing the pointed hat with a propeller - Dorothy's husband and child), exclaiming: "Oh my god, the hat." Turning the framed picture over, he notices Dorothy's marriage certificate to a man named Donald. Stunned to learn that she is a married woman (and his already-acquired knowledge that she is older, a mother, and a crazed masochistic nymphomaniac), he hides the photo again and leaves the apartment as Dorothy says one more time into her own reflection in the bathroom mirror: "Help me."

He descends the dark staircase outside the apartment building and the scene turns dark. The haunting and repulsive scene of Frank's victimization of Dorothy plays again in his mind as the loud, ominous sound of the ear howls on the soundtrack. Frank's orgasmic cries sound like the roar of a wild beast. An immense close-up of a candle flame burns and then is extinguished. When Frank slugs Dorothy in the face after she begs for the physical abuse ("Hit me"), Jeffrey is jarred from his nightmarish sleep in his bed, observing his room and moaning: "Man, oh man."

Wishing to share his troubled experiences with Sandy, Jeffrey calls her so they arrange to get together that evening. Parked in a car across the street from the town's white church, he fills Sandy in on the previous evening's events with a halted, troubled, broken delivery to describe Dorothy's nightmarish world:

Sandy (curiously): Well, aren't you going to tell me about it?
Jeffrey: OK. It's a strange world, Sandy. Dorothy Vallens is married to a man named Don. They have a son. I think the son and the husband have been kidnapped by a man named Frank. Frank has done this to force Dorothy to do things for him. I think she wants to die. I think Frank cut the ear I found off her husband as a warning for him to stay alive. Frank, is, uh, a very dangerous man.
Sandy (empathetically): My god. Shouldn't you tell my father?
Jeffrey: No. I can't do that. I can't prove any of this. I found out my information illegally. You could get into a lot of trouble.
Sandy: You saw a lot in one night. It's a strange world.
Jeffrey (troubled and anguished): Why are there people like Frank? Why is there so much trouble in this world?

To answer his question about pain, evil and unhappiness in life, while religious-sounding organ music plays on the soundtrack, Sandy shares a euphoric description of her own dream world, using imagery including robins and transcendent Love. She promises in her sermon that there will be an end to troubled times when the robins return to Lumberton to bring sunshine - an antidote to end the evil darkness:

Sandy: I don't know. I had a dream. In fact, it was the night I met you. In the dream, there was our world and the world was dark because there weren't any robins, and the robins represented love. And for the longest time, there was just this darkness. And all of a sudden, thousands of robins were set free, and they flew down and brought this Blinding Light of Love. And it seemed like that love would be the only thing that would make any difference. And it did. So I guess it means there is trouble 'til the robins come.
Jeffrey: You're a neat girl.
Sandy: So are you. (laughs) I mean, you're a neat guy.

As their car pulls away, the camera focuses on the church behind with its beautiful stained-glass windows and rising sound of organ music. As his relationship is budding with Sandy, Jeffrey is also being initiated into the dark, degrading world inhabited by Dorothy and Frank - he is dangerously attracted to the overwhelming power of sex and pleasure. The distinction between being a detective or a pervert vanishes as he becomes more of a participant than an observer of events.

In the next scene, Jeffrey boldly knocks on the door of apartment #710 at the Deep River Apartments, Dorothy's place. Their conversation leads to a sexual encounter as he becomes the bad-girl's lover:

Dorothy: Why are you here? What do you want?
Jeffrey: I, uh...
Dorothy: I looked for you in my closet tonight. It's crazy. I don't know where you come from, but I like you.
Jeffrey: It's not crazy. I like you too.
Dorothy: (She steps close to him.) I liked being with you last night.
Jeffrey: Same here. (They begin kissing.)
Dorothy: Please be with me. Be with me please.

The howling wind in her apartment is linked in the next scene to a strong wind blowing trash through the parking lot at the Slow Club. Jeffrey orders a Heineken beer while watching Dorothy sing her trademark song: "Blue Velvet." Jeffrey sits back when he spots Frank (at a nearby table shrouded in blue light from the stage) watching Dorothy perform. Wet-eyed Frank is totally mesmerized and captivated by her rendition ("...And I still can see Blue Velvet through my tears"), clutching, stroking, and working the torn blue swatch of her robe in his hand.

Outside the club, Jeffrey sits in his bright-red convertible, as storm clouds build and rumble in the background. Frank and a few of his criminal friends exit the club and enter a black car. Jeffrey moves out and follows them through the dark streets of Lumberton to an old apartment building that Frank frequents. Jeffrey noticed a name plate: "FRANK BOOTH."

The next scene is introduced with a slow pan across Jeffrey's convertible dashboard - a white rose, an empty Heineken beer bottle, crumbled bags of chips, and a banana peel, while the local radio station again plays its jingle: "Logs, logs, logs. Lumberton, USA. At the sound of the falling tree, it's 1:30, and this is the mighty voice of Lumberton, the town where people really know how much wood a woodchuck chucks."

Behind a chain-link fence across the street during an after-school football practice, Michael (Sandy's boyfriend) spies Sandy being picked up outside school by Jeffrey. Their second scene in Arlene's is again introduced by a logging truck passing in front of the local diner. At a booth, Jeffrey tells Sandy, in a flashback, about his surveillance as an amateur sleuth and how he has staked out Frank's suspicious activities where he lived during the day (when gangsters - and insects - are most visible and detectable). With a hidden camera taped and rigged to his car's dashboard and covered with a cardboard shoebox, he records and snaps pictures of Frank associating with the Yellow Man as they enter the brick building, and then shortly later, the Yellow Man's exit from the building with a mustachioed "Well-Dressed Man" with a briefcase. Jeffrey followed them in their car to a downtown factory where on a fire-escape stairway, they looked in the direction of a drug-dealing transaction that ended up as a gruesome murder-crime scene being investigated by the police - with one man dead (the drug-dealer was hanging from a window) and a blonde woman on the ground with broken legs (after being tossed from the building):

Jeffrey: See that clock on the wall...Five minutes from now, you're not going to believe what I've told you. Number One. Today, I staked out Frank's place with a camera. Now, there's another man involved in all this. I call him the 'Yellow Man'. You saw his back the other day at Dorothy's apartment. Today, I saw the Yellow Man go into Frank's building, laughing with Frank. Now, the only trouble is, what does that prove?
Sandy: Nothing really, but it's interesting.
Jeffrey: Number Two. I saw the Yellow Man come out and meet up with a well-dressed man carrying an alligator briefcase. They went to this factory building downtown, stood on a staircase and looked off into the distance. Now get this. In the distance, there was a murder - this drug dealer was shot to death and a woman had her legs broken.
Sandy: Jeffrey!
Jeffrey: And these two guys told me that the police would find a huge amount of drugs in the dead dealer's place.

The most intimate secret he doesn't share with Sandy involves his sexual desire and attraction to Dorothy and the alluring, dark world of the human psyche that she inhabits ("I'm seeing something that was always hidden"). Sandy offers warnings to Jeffrey, worried about his continued dangerous involvement into the sordid, insectile nightlife involving Dorothy and her criminal associates:

Sandy: I can't believe what you're finding out. Are you gonna continue with this?
Jeffrey: Yeah.
Sandy: Until when? I mean, what are you going to do with this stuff?
Jeffrey: Well, I don't know.
Sandy: You're not going back to her apartment. (Jeffrey nods with "Yeah") Jeffrey why?
Jeffrey: I'm seeing something that was always hidden. I'm involved in a mystery. I'm in the middle of a mystery and it's all secret.
Sandy: You like mysteries that much?
Jeffrey: Yeah. You're a mystery. I like you, very much.

Jeffrey stands and moves to her side of the booth. After staring at each other, Sandy tells him: "Oh yeah," and he leans over and kisses her gently. She pulls away, asking: "Jeffrey. Don't. Please."

Jeffrey: You worry about me really?
Sandy: Yeah. Is that so surprising? Yeah, I worry. A lot. I got you into this.