In a retro-futuristic rendition of the 1950s, a television host presents a documentary that delves into the creation and production of Asteroid City, a captivating play by the renowned playwright Conrad Earp. The events of the play are portrayed in vibrant widescreen color, while the accompanying television special is depicted in a classic black-and-white Academy ratio.
Set in the fictional desert town of Asteroid City, the narrative centers around a Junior Stargazer convention. The story unfolds as war photojournalist Augie Steenbeck arrives early with his intellectually curious teenage son, Woodrow, and his three younger daughters. Their journey takes an unexpected turn when their car breaks down, prompting Augie to contact his father-in-law, Stanley, who has a strained relationship with him. Stanley persuades Augie to reveal the truth about their mother’s recent passing, a truth that Augie had shielded from the children.
As the story progresses, Augie and Woodrow encounter Midge Campbell, a well-known yet jaded actress, who is accompanied by her daughter Dinah, also set to be honored at the convention. A romantic connection unfolds between Augie and Midge, as well as between Woodrow and Dinah, creating a tender subplot amidst the primary storyline. The convention attracts a diverse group of participants, including five-star General Grif Gibson, astronomer Dr. Hickenlooper, and a group of enthusiastic teenage honorees—Clifford, Shelly, and Ricky—along with their parents and a busload of elementary school children guided by the young teacher June Douglas. The accommodations for the attendees are provided by a local motel.
As the event commences, General Gibson welcomes everyone at the Asteroid City crater, where the teenagers are set to receive accolades for their innovations. Suddenly, a UFO disrupts the festivities, and an alien emerges, stealing a remnant of the meteorite that had formed the crater—an event that Augie captures on film. In response to this extraordinary occurrence and under orders from the president, Gibson imposes military quarantine on the town, subjecting everyone to thorough medical and psychiatric evaluations. Meanwhile, a budding romance develops between Montana and June, who comfort the students by assuring them that the alien is likely benign. Utilizing Dr. Hickenlooper’s equipment, the Stargazer honorees attempt to reach out to the alien. In a daring move, Ricky manages to divert the guard watching a payphone and contacts his school newspaper to leak details about the quarantine.
As the events in Asteroid City garner national attention, a furious Gibson faces pressure to lift the quarantine, but the UFO returns unexpectedly, placing the meteorite back in its original spot. Observing new markings on it, the General concludes that it has been "inventoried." Thus, he reestablishes the quarantine, inciting a rebellion from the children, scientists, and parents who band together using the honorees' inventions to counter the military's authority.
In an epilogue to the narrative, Augie and his family emerge as the last inhabitants to exit Asteroid City after Gibson formally ends the quarantine. Woodrow announces that he has secured fellowship funding, while Midge leaves Augie her contact information, offering a glimpse of potential for their future. Augie and his family retreat in silence from the town.
Layered throughout the movie is the interplay between the documentary of the play's creation and its live performance. In the story of the play's development, Conrad Earp meets with actor Jones Hall, who auditions in Earp's home and is promptly cast. Their relationship evolves into a romantic partnership as they share a kiss. Earp crafts the play with assistance from a local acting school, casting many of the performers from there, including Mercedes Ford, an emotionally charged yet talented actress portraying Midge.
During the recorded performance, Hall, who takes on the role of Augie, confronts director Schubert Green, confessing he "still doesn't understand the play" and questioning whether he is "doing him right." Green encourages Hall to maintain his portrayal of Augie, reassuring him despite his doubts. Following this exchange, while on a break, Hall encounters the actress originally meant to play his wife, who recites her cut scene’s lines, prompting a fresh perspective for Hall.
Tragically, amidst the play’s success, Conrad Earp loses his life in a car accident six months into its run.
