Kit's killing spree is instigated by Mr. Sargis' refusal to let him have a relationship with Holly, and by the killing of her dog. That evening, Kit cautiously approaches Holly's house and slips in after knocking, at about the same time that the over-protective Mr. Sargis picks up Holly from her music school. In Holly's upstairs bedroom, Kit packs her suitcase to take her away - with a gun visible in his back right jeans pocket.

When Mr. Sargis arrives home and is surprised by the unexpected visitor, he is first visible in the dresser's mirror - his reflection comes from the end of the hallway outside the bedroom. Kit brandishes his pistol, an alternative for his unsatisfying sexual ability, as Holly's father angrily orders him from the house. While Holly (in a light blue dress with puffy sleeves) stands and watches impassively, Kit announces that he's "got it all planned - and, uh, I'm taking Holly off with me." When Mr. Sargis descends back down the stairs and threatens to turn him over to the authorities for trespassing with a gun, Kit protests: "...I can't allow it." At the foot of the stairs in the living room, Kit follows him and asks: "Suppose I shot you. How'd that be? Huh? You want to hear what it sounds like?" After firing a warning shot, Kit rushes down the stairs and fatally shoots Holly's father twice in the stomach, in cold blood, in the middle of the living room. Non-chalant killing without a twinge of conscience, emotional involvement, or remorse comes easily for the catatonic young man. His gun swiftly eliminates the small obstacles or nuisances that hinder the fulfillment of his willful dreams.

As evening arrives, Kit drags the body into the cellar. He finds a discarded toaster and takes it upstairs. When he apologizes, she only slaps him hard across the forehead - an unusual, emotionless, inappropriate, and amoral reaction to the murder of her single parent. In the living room, he convinces her that she shouldn't contact the police:

Holly: Listen, maybe we ought to tell somebody about this.
Kit: You said that once already. Too late now.
Holly: Why?
Kit: They're not gonna listen to me. You either. Are you kidding?
Holly: Suppose the neighbors heard the noise?
Kit: Wouldn't be funny. Listen, uh, I'll be back after a while. (He approaches the front door.) Oh, uh, you want to call the police, that's fine. Just won't be so hot for me. (They exchange a parting glance.)

While Kit is gone, Holly acts emotionally detached and passive, although she has already implicitly agreed to tag along with Kit for the 'ride' [and betray the memory of her father]. She smokes a cigarette and walks upstairs to her bedroom, ready to become Kit's good-girl-gone-bad partner. From her window, in a contrasting scene, she watches two young boys under a streetlamp playing an innocent game - they secretly share something with each other.

At the town's almost-deserted train station, Kit has entered a VOICE-O-GRAPH private recording studio booth and inserted fifty cents into the machine to record a vinyl record at 45 rpms. [This is the first of two instances of his recording his thoughts without writing them down. Evidently, Kit is almost illiterate.] He narrates a fake-suicide testimony that will be left at the house for the authorities to find:

My girl Holly and I have decided to kill ourselves, same way I did her Dad. Big decision, huh? Uh, the reasons are obvious, and I don't have time to go into them right now. But uh, one thing, though. He was provoking me when I popped him. That's what it was like, a Pop! We're sorry, I mean, uhm, nobody's coming out of this thing happy, especially not us. I can't deny we've had fun, though. I mean, uhm, that's more than I can say for some. That's the end of the message. I run out of things to say. Thank you.

Back at Holly's house, he douses the entire interior of the house with gasoline poured from a ten-gallon can. Both Kit and Holly collect items to take with them (a suitcase, a painting, a lamp). Before setting the house on fire and fleeing the murder scene, Kit sets up a victrola on a table in the back yard and puts the needle on the record to play again and again (Holly's voice-over: "Kit left a record playing over and over for the District Attorney to find. He was gambling for time.") As they drive away, a montage of items burning in the conflagration are seen as they are lyrically consumed by flames: a framed picture on the stairs, the peacock feathers, a cantaloupe and a pomegranate on the kitchen table, Holly's bedroom and a doll on the bed, Holly's doll house, a sign outside the house, Mr. Sargis' corpse, the piano in the living room with sheet music, a watering can and spoked wheel. A man surveys the burning embers of the house with a flashlight.

Detouring from their flight early the next morning, Kit insists on driving Holly by her high school, where he allows her to pick up her books from her locker, so that she won't "fall behind" - how extraordinarily practical and bizarre! Holly contemplates sneaking away, but then accepts her "destiny" with Kit - to join him for an adventurous odyssey that would prevent "years of loneliness." They pick aliases for themselves (James and Priscilla) that they don't use, and plan to "hide out like spies" -- a tip-off that star-struck Holly is play-acting within an adventure movie that is running inside her mind:

Kit made me get my books from school, so I wouldn't fall behind. We'd be starting a new life, he said. And we'd have to change our names. His would be James. Mine would be Priscilla. We'd hide out like spies, somewhere in the North, where people didn't ask a lot of questions. I could of snuck out the back or hid in the boiler room, I suppose, but I sensed that my destiny now lay with Kit, for better or for worse, and it was better to spend a week with one who loved me for what I was than years of loneliness.

Their first primitive hideout and shelter is by the riverbank in a cottonwood grove - in an elaborate, multi-storied treehouse that they construct out of tree branches, planks, and tamarisk branches. In another montage, the survivalists and partners-in-crime devise various warning systems, code words, and booby traps (a swinging ball of spikes that is triggered by string laid across the path), knowing that sooner or later, the police will come looking for them. Kit sleeps with his pistol by his side, with Holly close by and next to the box of shells (her hand quivers). He exhorts them to rigorously train and exercise to be prepared for an intrusion from any outside 'enemy':

We hid out in the wilderness down by a river in a grove of cottonwoods. It being the flood season, we built our house in the trees, with tamarisk walls and willows laid side by side to make a floor. There wasn't a plant in the forest that didn't come in handy. We planned a huge network of tunnels under the forest floor, and our first order of business every morning was to decide on a new password for the day. Now and then, we'd sneak out at night and steal a chicken or a bunch of corn or some melons from a melon patch. Mostly, though, we just lay on our backs and stared at the clouds and sometimes it was like being in a big marble hall, the way we talked in low voices and heard the tiniest sound. They hadn't found but one set of bones in the ashes of the house, so we knew they'd be looking for us. Kit made sure we'd be prepared. He gave me lectures on how a gun works, how to take it apart and put it back together again, in case I had to carry on without him. He said that if the Devil came at me, I could shoot him with a gun.

One day, they stroll-dance to the tunes ("Love is Strange," sung by Mickey and Sylvia) emanating from their portable radio. During their improbable and often icy relationship that they have while 'playing house,' Holly compares them to any ordinary loving couple that bickers from time to time. They pass the endless days by catching fish with a forked-stick net (handmade from sticks and twigs), cutting or toting firewood, listening to Holly reading portions of Kon-Tiki outloud, watching the animals and other life-forms in the forest, or reading old issues of National Geographic Magazine:

We had our bad moments, like any couple. Kit accused me of only being along for the ride, while at times I wish he'd fall in the river and drown, so I could watch. Mostly though, we got along fine and stayed in love. I grew to love the forest. The cooing of the doves and the hum of dragonflies in the air made it always seem lonesome and like everybody's dead and gone. When the leaves rustled overhead, it was like the spirits were whispering about all the little things that bothered 'em.

While viewing sepia-toned, stereopticon slides ("vistas") of a past idyllic time of famous monuments and various family groupings (of a palm-fringed canal in Rio de Janiero-Brazil, a boy on a camel in front of the Sphinx in Egypt, of cows standing in a fjord with a steamship in the background, of a young mother with her child, of a woman playing sheet music at a piano with another woman watching, a family gathering on a lawn, and a soldier whispering words into the ear of his girlfriend standing in a wheatfield), Holly speaks profound truths about the mysteries of the march of time toward death:

One day, while taking a look at some vistas in Dad's stereopticon, it hit me that I was just this little girl, born in Texas, whose father was a sign painter and who had only just so many years to live. It sent a chill down my spine, and I thought - Where would I be this very moment if Kit had never met me? Or killed anybody? This very moment? If my Mom had never met my Dad? If she'd of never died? And what's the man I'll marry gonna look like? What's he doing right this minute? Is he thinking about me now, by some coincidence, even though he doesn't know me? Does it show on his face? For days afterwards, I lived in dread. Sometimes, I wished I could fall asleep and be taken off to some magical land, but this never happened.

One day when he becomes frustrated while fishing with his hand-woven lacrosse-stick net, Kit abandons his peaceful harmony with the natural world. He fires his weapon at a fish underwater - and is spotted by a man on the other bank of the river - his reckless action results in expulsion from the Edenic natural paradise. Later that day, Kit sees from the crow's nest of the treehouse that there is a person moving through the brush and that they have been discovered. With a coded yell, he signals to Holly (who is putting on makeup) in the forest to hide ("Run, somebody's comin', hide"), and then dives under a hole in the ground that is covered with leaves. As the three western-dressed men, armed with guns, walk over his hiding place, he ambushes them. He fires at two of them from behind and kills them. He pursues the third man and shoots him in the back. Before driving away from their temporary home, Kit tosses away a birdcage and frees their rooster from its wicker enclosure. In voice-over, Holly reveals how the code that they live by constantly changes - killing bounty hunters is acceptable, but killing lawmen is not. She is told by her cold-blooded killer-lover that they were attacked by bounty hunters:

Kit felt bad about shooting those men in the back, but he said they'd come in like that, and they would've played it as down and dirty as they could. And besides, he'd overheard them whispering about how they were only interested in the reward money. With lawmen, it would've been different. They were out there to get a job done and they deserved a fair chance. But not a bounty hunter.

They drive over a flat field to the isolated, solitary farm where Cato, Kit's garbage-route co-worker, is living: (Holly's voice-over: "We went to hide out with a friend of Kit's from the days of the garbage route.") A set of deer antlers are mounted over the outside of the door of the place that Cato is "running" for a fella in town. Cato doesn't know what to make of the unpredictable Kit with his "girl" Holly, and attempts to appease them. Outside under a tree, Cato shares a picnic lunch with them of the live chicken that Kit brought with them - Holly drinks milk while Cato and Kit drink beers. Afterwards, they walk out toward a field where Cato claims a boy found some old Spanish coins while plowing the ground. When Cato turns and runs back to the house to allegedly retrieve a shovel (is he attempting to escape?), Kit quickly becomes suspicious and shoots him through the stomach.

Kit never let on why he'd shot Cato. He said that just talking about it could bring us bad luck and that right now, we needed all the luck we could get.

Kit obligingly opens up the front door for Cato, who stumbles into the interior of the cluttered house. He falls onto his bed and remains motionless and terrified. Holly's question to Kit about Cato is unbelievably disquieting: "Is he upset?" Children of the television generation of the 50s, both Kit and Holly calmly watch and converse with the dying man as he complacently lies there and slowly bleeds to death.

Unexpectedly, a Studebaker drives up to the house, and the young male driver named Jack (Bryan Montgomery) (with his girlfriend (Gail Threlkeld)) asks to see Cato. Kit lies to them about Cato's whereabouts and refuses to let them into the house: "You go in there, I'll have to kill you...Can't afford to take chances." He leads Jack into a nearby field toward a distant storm cellar. Holly follows behind with the girl, as if she were her schoolyard friend, and makes casual small talk (although she must know that an execution is imminent). Holly asks about their relationship and whether she loves Jack:

Girl: What's going to happen to Jack and me?
Holly: You have to ask Kit. He says 'frog,' I jump.
Girl: OK.
Holly: What's your friend's name?
Girl: Jack.
Holly: You love him?
Girl: I don't know.
Holly: I've got to stick by Kit. He feels trapped.
Girl: Yeah, I can imagine.
Holly: Well, I've felt that way, hadn't you?

In the middle of the vast expansiveness of the area, the girl expresses uncertainty about her relationship with the boy, in contrast to Holly's ironic yet 'reasoned' loyalty to her "trapped" boyfriend. After imprisoning the couple inside the storm cellar and forcing them to promise to stay there for at least an hour, Kit secures the latch and then fires two shots at them through a hole in the door - possibly killing them. Again, Holly cooperatively stands by and watches as the carnage mounts - she senses the volatility of her "trigger happy" boyfriend:

Suddenly, I was thrown into a state of shock. Kit was the most trigger happy person I'd ever met. He claimed that as long as you're playing for keeps and the law is coming at ya, it's considered OK to shoot all witnesses. You had to take the consequences, though, and not whine about it later. He never seemed like a violent person before, except for once, when he said he'd like to rub out a couple of guys whose names he didn't care to mention. It all goes to show how you can know a person and not really know him at the same time.

Kit carries and dumps Cato's body in a box-car near the house, and Holly remarks: "We're in for it now, if they catch us." Kit nonchalantly and defensively tells Holly the unlikely reason why he moved Cato's body: "Just to keep him out of the sun." Kit is surprised at his own impulsiveness - he walks back and forth behind the box-car, out of view of Holly, where he expresses his agitated and frustrated state of mind.

As they drive away and leave behind a second murder scene, Holly muses about how desensitized she has become to their trail of violence:

At this moment, I didn't feel shame or fear, but just kind of blah, like when you're sitting there and all the water's run out of the bathtub.

When they drive past a wrecked vehicle lying in a roadside ditch, the anger-driven Kit imagines that he will also be blamed for it: "They're probably gonna blame that on me, too, bastards!"