From the wikipedia entry:

The story opens with an unnamed grandmother complaining to her son, Bailey, and his family that she would rather go to Tennessee for vacation than Florida, the family’s planned destination. After the family resolves to go to Florida regardless of her protests, she spites them by rising early the next morning and waiting in the car for the rest of the family, dressed in her Sunday best, so that if she should die in an accident she will be recognized as “a lady.”

The grandmother talks incessantly during the trip, recalling her youth in the Old South and commenting on various things she sees alongside the road. When the family stops at a gas station/diner, called “The Tower,” for lunch, she engages the owner, Red Sammy, in conversation about the state of the world’s affairs, specifically an escaped convicted murderer known only as “The Misfit.” The grandmother agrees with Red Sammy’s assertion that a good man is increasingly hard to find.

Back on the road, the grandmother, trying to detour the family away from Florida, begins telling stories about her nearby childhood home. Upon hearing that it has secret passages, the children become fixated on visiting the house, and the grandmother instigates them to pester their father until he gives in and agrees to follow the grandmother’s directions to the house. When the grandmother’s directions lead them down an abandoned dirt road, she realizes that the house is, in fact, in Tennessee and not Georgia. Flustered, she upsets her cat, which panics and attacks Bailey, causing him to lose control of the car and roll it into a ditch.

No one is seriously injured, and the children are inclined to view the accident as an adventure; not wanting to face the consequences for giving the family improper information, the grandmother feigns an internal injury in order to gain their sympathy.

The family waits for a passerby so that Bailey can get help. Not long after the accident, a car pulls up and a pair of men get out, wearing clothes that are clearly not their own and led by a shirtless, bespectacled man with a gun. The man in glasses instructs his cohorts to inspect the family’s car and engages Bailey in polite conversation until the grandmother identifies him as the Misfit. As the Misfit instructs his accomplices to murder the family one by one, the grandmother begins pleading for her own life, first reminding the Misfit that she is an old woman and therefore unworthy of death, and then by flattering him. When the Misfit ignores her pleas, she becomes speechless for the first time in the story. Panicked, she attempts to witness to the Misfit about Jesus. The Misfit becomes visibly angry and outlines his philosophy on life: that he is angry with Christ for having given no lingering, physical evidence for His existence, therefore casting doubt about the legitimacy of Christianity. The Misfit explains that he is angry because he does not want to waste his life serving a figure who may not exist, nor does he want to displease an almighty God who may exist; frustrated by the paradox, he has settled on the idea that “There’s no pleasure but meanness.” The grandmother then reaches out to the Misfit, calling him her “child,” prompting the Misfit to violently recoil and brutally shoot her three times.

When the Misfit’s accomplices finish murdering the family, the Misfit takes a moment to clean his glasses and assess the grandmother, concluding that “she would have been a good woman . . . if it had been somebody there to shoot her every minute of her life.” When one of his accomplices comments on the fun that they’ve all had murdering the family, the Misfit angrily reprimands him, telling him, “It’s no real pleasure.”