Modeled on the classic 18th-century picaresques like Fielding's The History of Tom Jones, a Foundling and Defoe's Moll Flanders, The Life and Adventures of Lyle Clemens is the modern-day bildungsroman of a prodigiously attractive young Texan named Lyle Clemens. Lyle is kind of a holy fool who, like Chance in Being There, illuminates the actions, motivations, and prejudices of others through his lack of cynicism. He is a simple babe, in the woods of Texas and Los Angeles.
Lyle's mother, Sylvia, is a beautiful woman who was raised Pentecostal and rebelled against her mother through sexuality--but her dreams to become Miss America were dashed by her mother in a particularly traumatic way, and Lyle's father (Lyle the First, a dashing cowboy), who consoled her in her time of need, left her when she became pregnant, leaving only money for an abortion Sylvia never got. Sylvia never talks about her own childhood or Lyle I, and takes refuge in alcohol; an entertaining Chicana Catholic kook named Clarita, given to religious visions and wacky pronouncements, helps Sylvia raise Lyle. Despite his unusual circumstances, Lyle has a sunny disposition. Like his father, Lyle is given to wearing cowboy boots and other Western attire, and often has to explain to people that he's never actually ridden a horse.
Things come to a head when Lyle reaches sexual maturity and falls in love with a girl in his school--a beautiful young Chicana named Maria. Unfortunately, Maria's father Armando was one of Sylvia's boyfriends and thinks he is Lyle's father. Sylvia, out of vague sexual possessiveness toward her son, colludes with Armando to keep them apart, though she knows in her heart Lyle I is the father. The Pentecostals who fought to keep Sylvia in the fold all those years ago come back to town and, desperate, Sylvia takes Lyle to a tent revival. She quickly comes to her senses and realizes she has no place there, but they are already smitten with Lyle's amazing good looks, beautiful guitar-playing and singing, and natural charisma. They begin to recruit him to come to Los Angeles to join their Pentecostal televangelism empire.
Alienated from Maria and fed up with his mother, Lyle decides it's time for him to strike out on his own, so he follows "Brother Bud and Sister Sis" to L.A. A black woman named Matilda of the Golden Voice, now alienated from Bud and Sis, encourages his musical gift but warns him obliquely not to trust Bud and Sis. Quickly Bud and Sis begin grooming Lyle as the newest Christian star sensation, dubbing him "The Lord's Cowboy."
Meanwhile, a desperate and vain B-movie actress named Tarah Worth is angling to make a comeback. She hears she is up for the role of Helen Lawson (the older, washed-up actress character) in a sequel to Valley of the Dolls. Shortly after arriving in town, Lyle has taken a job working at a party at the Playboy Mansion, and saves Miss Millennium (a Playmate) from a feral peacock. He becomes known around L.A. as the "Mystery Cowboy" and Tarah hatches a plan in which Lyle will be framed for kidnapping her, that she feels will assure her the Valley of the Dolls role.
One of Lyle's friends from Texas, a gay kid named Raul, shows up in L.A. Bud and Sis are none too thrilled that their charge is trusting his gay friends and Sister Matilda over them, and he breaks from them on-air during their televangelist show--which they play off as demonic possession. Lyle attempts to keep Raul from getting bilked by sketchy pornographers, and to otherwise protect him from the seedier elements preying on gay street kids in L.A. Maria shows up in town to announce that she still loves Lyle, sleep with him one last time, and then inform him she's marrying a business contact of her father's for money. Lyle feels betrayed and tells her he never wants to speak to her again.
Most dramatically, Lyle finally meets his father. Having been told he's an abandoning son-of-a-bitch his entire life, he's very angry and hostile but there is some closure and a hint of rapprochement. He also learns from a letter from Clarita that his mother's difficult life is over, and gains some insight into her childhood. The end comes when he re-encounters Sister Matilda, now preaching on the street comparing her father's lynching to the Crucifixion, and takes her to lunch at Musso & Frank's. Feeling a sense of great tragedy and change, he takes off his clothes and, on a busy street in L.A., does the preacher strut and sings "Amazing Grace" as a tribute to his mother, jeered by passersby.