Jeffrey peeking from inside Dorothy's closet.

Jeffrey Beaumont is the protagonist in David Lynch's seminal 1986 film Blue Velvet. He is a friendly, snoopy, well-to-do college student who has returned to his hometown of Lumberton, North Carolina, after his father becomes ill from a mystery illness. After visiting his father, he comes across a severed human ear among a grass field. Jeffrey decides to get involved with the case. With the assistance of high-schooler and childhood friend Sandy Williams, the two put together clues from her father, Detective John Williams, who is investigating the ear. Sandy tells Jeffrey of someone whose name she frequently overhears in her father's phone conversations with fellow police officers: lounge singer "Dorothy Vallens", who lives in an apartment complex near Sandy. Jeffrey, increasingly curious, devises a plan to access Dorothy's apartment while posing as a bug terminator, and then find a key to break into her apartment.

After retrieving the key, Jeffrey and Sandy watch Dorothy perform at the Slow Club, and then head to her apartment. Sandy keeps watch in the car while Jeffrey searches her apartment; however, Jeffrey does not hear Sandy's car horn signaling Dorothy's return. Upon her entrance, he ducks into her living-room closet, though she eventually finds him. Having briefly undressed in view of Jeffrey, Dorothy takes him for a pervert, and forces him to strip at knifepoint as revenge. Dorothy then makes sexual advances toward a shocked, unconsenting Jeffrey. However, the two are interrupted by a knock at the door. Dorothy forces Jeffrey to run and hide in the closet, threatening to kill him if he makes any noise. Through the closet, he watches Dorothy as she is brutalized and raped by psychopath Frank Booth. After Frank has left, Jeffrey tries to console Dorothy, only to be propositioned again. He reluctantly accepts Dorothy's advances, beginning a questionably healthy liaison with her.

After investigating further, Jeffrey finds that Frank, leader of Lumberton's underworld of crime and prostitution, has kidnapped Dorothy's husband and son. While he holds them captive, Dorothy will do anything she wants for Frank, lest he kill both her husband and her son. Frank had cut the ear off of the husband as a warning to Dorothy, and had dropped it in the grass field where Jeffrey found it. Also seen with Frank and Dorothy is the former's associate, the "Yellow Man," who Jeffrey later learns is a corrupt police investigator and Det. Williams' partner at the police station. Having been found together in her apartment, Jeffrey and Dorothy are forced to ride with a recklessly-driving Frank and his company. When Frank begins to abuse Dorothy right in front of him, Jeffrey punches Frank in the face. Frank's friends drag Jeffrey out of the car and hold him still as Frank threatens his life and severely beats him. Left on the side of a dirt road, Jeffrey walks back to his house in the morning.

Jeffrey stops by Sandy's place in the evening to take her to her classmates' house party, and tells Det. Williams what has been going on. The detective sternly instructs Jeffrey not to involve himself any further. He leaves for the party with Sandy, where they slowdance and kiss, despite her having a boyfriend. On their way back, a car begins riding up on their tail; fearing its driver is Frank, Jeffrey refuses to pull over until they reach his house. They are confronted by the driver, who is actually Sandy's enraged boyfriend, until they see Dorothy naked and left for dead in Jeffrey's lawn. The Beaumonts and Sandy usher her in, only for a delirious Dorothy to tell Sandy that Jeffrey "put his disease in" her. A heartbroken Sandy slaps Jeffrey, but forgives him over the phone that night, after he discloses all of he and Dorothy's relationship.

Defying Det. Williams' orders for Dorothy's sake, Jeffrey rushes to her apartment in hopes of rescuing her son. He is instead met with the horrific scene of Dorothy's husband, bound to a chair and shot in the head; and the Yellow Man, whom Frank has crudely lobotomized. Booth flees to the apartment after the police raid his own home, and overhears Jeffrey calling for help on the Yellow Man's police radio. Realizing that Frank has a police radio as well, and is coming for him, Jeffrey intentionally gives the police false information as to his whereabouts to throw Frank off his trail. Jeffrey grabs the Yellow Man's gun and returns to the closet. Frank enters the apartment, kills the Yellow Man, and then seeks out Jeffrey, who had claimed over radio to be in the bedroom. Turning up emptyhanded, Frank remembers having found Jeffrey in the closet the night prior, and apprehensively approaches. He opens the closet door to find himself at gunpoint. Jeffrey shoots a surprised Frank in the head, killing him.

At the end of the film, an older Jeffrey is seen lounging on a chaise next door to his family's house, from which his recently-recuperated father waves to him. Sandy, now presumably his wife, bids him in for lunch; and he and his family join her inside.