The Miss Firecracker Contest is set in Brookhaven, Mississippi during the midst of Carnelle's attempt to salvage her tarnished reputation as "Miss Hot Tamale" through entering the Miss Firecracker Contest, the town's annual beauty pageant held on the Fourth of July. Carnelle, who is an orphan, was taken in by her Aunt Ronelle and raised with her two cousins, Elain and Delmount. Aunt Ronelle died of cancer after receiving a pituitary gland transplant from a monkey, causing her entire body to grow long black hairs. Elain won the Miss Firecracker pageant at the young age of 17, compared to Carnelle who pushes the pageant age limit of 24. Elain married well, using her beauty to win a husband after junior college. Delmount was admitted to a mental institution and has been involved in quite a few scandals with exotic beauties who catch his eye. Carnelle recently recovered from syphilis, though not before giving it to the sickly Mac Sam. Carnelle has been attempting to redefine herself by volunteering for the cancer society, attending church, and taking an orphan to dinner every week. She now plans to win the Miss Firecracker Contest to prove to everyone in Brookhaven that she is a valuable and beautiful young woman.
The play opens with Carnelle practicing her skit in her living room for the talent section of the pageant. Carnelle is a 24-year-old self-conscious woman with a tarnished reputation. Growing up, Carnelle developed self-esteem issues which caused her to seek the company of many men and eventually contract syphilis. Her past promiscuity earned her the nickname "Miss Hot Tamale," and in an effort to dissociate herself from her past Carnelle wants to be crowned Miss Firecracker at the upcoming pageant. Popeye, a 23-year-old quirky seamstress, arrives to take her measurements for the contest. Popeye earned her nickname by accidentally putting ear drops in her eyes as a child which caused them to swell. Popeye herself is quiet, shy, and impressionable, shown when she falls in love with Delmount after only seeing his picture. Carnelle and Elain then discuss the beauty pageant and Carnelle's chances of winning. Elain is Carnelle's beautiful first cousin who previously won the title of Miss Firecracker and has continued to be remembered for her beauty. Encouraged by her mother, Elain went to junior college and capitalized on her beauty to marry a wealthy man and while she appears to have the perfect life, Elain is unhappy and narcissistic. Elain confides in Carnelle that she has left her family. Delmount arrives to an empty living room, and Popeye meets Delmount. Delmount is Carnelle's 28-year-old cousin and Elain's brother. He has a history of violence, and pleaded insanity to avoid a jail sentence after hitting a man in the face with a glass bottle. Elain refused to take custody of him, so Delmount remained in the asylum longer than was originally intended. As a result, Delmount and Elain often butt heads. In addition, Delmount has strange recurring dreams about dismembered and deformed women's body parts, and has a strange obsession with beauty. Delmount explains to Carnelle that Aunt Ronelle's house was left to him and he intends to sell it and all of its contents. Elain and Delmount get into a heated debate about Delmount's criminal history and time in the asylum. Delmount tells Carnelle he intends to give half of the profits made from the house to her, and Carnelle eventually takes to the idea, inspired by the prospect of "leaving in a blaze of glory" after she wins the pageant.
As Delmount sets prices for the items in the living room, he and Elain argue about the past. The two reveal that Carnelle has not received a telephone call yet saying she is a finalist for the pageant. Although Delmount thinks the pageant is ridiculous, he still feels sorry for Carnelle. Elain tells Delmount she is leaving her husband, and Delmount is very happy because he does not like Franklin, though he suspects that Elain is not completely sincere. They discuss their mother, Carnelle's Aunt Ronelle, and her shortcomings as their caregiver. Popeye enters and tells Elain that her "heart is hot" and that she believes she is in love with Delmount. Elain is surprised to hear this and tells Popeye that Delmount is not sane. The phone rings and Carnelle answers it, finally receiving news that she is a finalist for the pageant.
The scene opens in a dressing room at the beauty pageant. Carnelle tells Tessy that she needs Popeye to fix her dress. Tessy is the 23-year-old coordinator of the Miss Firecracker Contest. Her twin sister is a contestant in the pageant, although neither of the women are attractive. Despite this fact, she has a history with Delmount, and flirts with him at the pageant. Mac Sam, Carnelle's 36-year-old ex-lover, is the balloon man at the pageant and visits her in her dressing room. They discuss the fact that Carnelle gave him syphilis and he has not been treated for the disease. In addition to syphilis, Mac Sam has a plethora of other diseases, all of which he refuses to treat medically simply because he has lived longer than he expected without treatment. After Mac Sam leaves, Delmount informs Carnelle that the house auction went well. Carnelle tells Delmount that Popeye has feelings for him, and Delmount becomes agitated. Elain enters with the news that Popeye is missing and thus cannot fix the dress, but she has brought a Mardi Gras mask that Carnelle can use to hide the poor alteration. Carnelle receives a frog suit from Mac Sam and realizes that Popeye is somewhere close by, so Carnelle and Elain leave to find her. Popeye tries to fix the dress in their absence. Mac Sam, Carnelle, and Elain all come back to the dressing room, and Carnelle panics because the dress cannot be fixed without scissors. The others calm her down and then she finishes getting dressed.
Mac Sam and Delmount discuss the pageant and their views on beautiful women. Popeye and Elain reveal that Carnelle tripped while wearing the red dress, and consequently the audience began to laugh at her and call her names. Delmount is furious at one man in particular and exits with intent to fight him. Carnelle appears and feels humiliated. Carnelle does not feel confident in her chances of winning. After Carnelle leaves, Delmount and Elain explain that they are reluctant to watch Carnelle humiliate herself further. Elain receives flowers from Franklin and tells Delmount she is returning to her family, which makes Delmount very angry with her. Carnelle reappears, happy because the crowd loved her act. Carnelle then nervously departs for the crowning. Alone, Delmount further criticizes beauty pageants. Mac Sam, Elain, and Popeye come back to the dressing room after Carnelle loses the pageant. Carnelle follows after them and loses her temper with everyone. Tessy informs Carnelle she has to follow the parade carrying a flag, which Carnelle readily does.
Elain arrives back in the dressing room slightly drunk. She and Delmount make amends. Elain leaves to have a fling with a man. Popeye and Delmount discuss the future, and Delmount invites Popeye to watch the fireworks with him. The two of them leave before Carnelle arrives once more. Carnelle is surprised when Mac Sam appears next, and explains that in her absence she was by the railroad tracks thinking about her life. Mac Sam says he does not regret the times he spent with her, then departs. Delmount and Popeye climb up a tent to watch the fireworks. Delmount and Popeye invite Carnelle to watch the show with them. While she is climbing up, Delmount kisses Popeye and tells her he loves her. Carnelle reaches the top and explains that she realized that the beauty pageant was not that important after all. The play ends with the three admiring the fireworks.