As the opening scroll tells us, Narcotic was "presented in the hope that the public may become aware of the terrific struggle to rid the world of drug addiction." The movie itself is a salacious plunge into a world of sordid pleasures. It tells us the story of Dr. William G. Davies, an infamous snake-oil salesman who started his career as a promising medical student. In the opening sequence he saves an unborn baby by performing a cesarean operation after the mother was killed in an automobile accident. Stock medical footage shows a woman's stomach being sliced open like a ripe watermelon and the baby popping out like a jack-in-a-box. But the allure of opium proves too strong for the doctor to resist. After a single night of relaxation in a Chinatown opium den, Davies becomes a slave to drugs. As his medical practice deteriorates, he shifts his attention to "selling medicine by demonstration." He says to his nurse/fiancee, "I can't see anything wrong if my preparation has merit." However, his "preparation" is one of the great quack cure-alls: "Tiger-Fat." Davies soon becomes one of the leading sideshow attractions for a carnival. His success as a carnival huckster initially allows him to run with a fast crowd. In the movie's most shocking episode, Davies and his ritzy friends retire to a hotel room together for a drug party. "We're gonna get lit," says a woman. A buffet of drugs is spread out on a table and each guest takes their drug of choice. "It takes a needle for me to get a bang," says a woman. As each participant indulges, the party quickly turns into an orgy of excesses, one woman hikes up her skirts, another laughs hysterically, a man pontificates, another man becomes paranoid. The movie provides a litany of different reactions to drugs. Ultimately, Davies' drug addiction leaves him gaunt and stooped, living in a hovel with no hope of returning to his previous life.
- William G. Davis, a top medical student, arm wrestles a colleague in his dorm room where he relaxes with other students. One of them, G. Woo, speaks of opium as a harmless diversion for Chinese people, but cautions that Westerners, overwhelmed by progress and speed, might make any diversion into a vice.
In the next scene, a pregnant woman is killed when a speeding car smashes into the horse-drawn vegetable cart in which she rides. Davis, who now works at a free clinic, delivers her baby alive through a Caesarian operation, which leads an older colleague to state that Davis will go down in history.
Davis is soon overwhelmed in his work. G. Woo visits and encourages him to unburden himself in a diversion. He takes Davis to an opium den, and later, when Davis is worried over a bill for digging a cesspool, he returns to the den to smoke.
Davis soon marries his nurse, but he becomes fascinated by the drug and continues to visit the den. After he sees a hawker demonstrate a new glue called "Gooey Mooey," Davis avidly reads a book about selling technique. Worried about his obsession, Davis' wife reads a book about narcotic addiction, and she is greatly upset when she comes across the platitude, "You can take it out of the body, but not out of the mind."
When Davis excitedly tells his wife that he wants to sell a new "miracle cure" formula he has developed by hawking it in public, she argues that this would be unethical. Davis, however, goes ahead with his idea, and his wife visits a federal narcotics agent with G. Woo to get help. The agent reveals that drugs always find the weakest part of a person's character to attack, while Woo advises that only the will to be cured will lead to a cure. Davis' wife burns her husband's pipe and other paraphernalia, and Davis is admitted into a hospital. Afterwards, he proclaims to his wife that it will be wonderful to begin again.
During an emergency call, Davis is driven by a drug addicted taxi driver, who collapses after surreptitiously drinking a vial from Davis' medical case. The cab is hit by an incoming train killing the driver and seriously injuring Davis. To relieve Davis' pain, a doctor prescribes opiates, and Davis' addiction revives. After an argument, his wife leaves him, and Davis joins a traveling freak show hawking his cure-all, "Tiger Fat."
With the money he coerces out of his "patients," Davis and his gang have a "dope" party in a bordello with a number of women, during which participants sniff cocaine and inject heroin.
Sometime later, Davis violently awakens one of the half-dressed women and demands "where's the stuff" and "where's the money." When she reminds him that he gave her money to buy clothes, he calls her a "dirty trollop," rips her dress and storms out. Davis goes to the sideshow and demands the money from his cohorts. A brawl ensues, during which various snakes and skunks are freed as their cages are knocked over. One snake devours another.
In his apartment, Davis locates some hidden drugs and a gun. He sniffs the drug and lies back remembering scenes from his life. A knock awakens him, and a man enters and rebukes him, calling him a disgrace to society and a mental and moral coward. Alone, Davis talks to himself and to God. He cries and then shoots himself dead.