All the townspeople assemble in the church for Sunday service, from the town beauty to the "Model Boy". Reverend Sprague begins offering prayers for virtually all the world's citizens.
Sunday is a sacred day for all of St. Petersburg, when the entire village goes to church to convene as a community of shared values. In their gathering, Twain spotlights the stereotypical characters that make up small-town America.
It is the same sermon Mr. Sprague offers every week. Tom loses interest and becomes absorbed in the behavior of a resting fly. He yearns to catch it, but doesn't dare to for fear that interrupting the prayers will damn him. When the reverend finally says Amen, Tom instantly grasps the fly. Aunt Polly makes him let it go.
Even though Tom isn't interested in learning the Bible, he believes in the worst stories he has heard of hell. Furthermore, his sense of self-importance is so heightened that he fears he might be considered the greatest of sinners for even a minor sin.
The reverend sermonizes about the apocalypse. Tom wishes he could be its hero, braving "limitless fire and brimstone". Any moral lessons are lost on him, however.
For Tom, even hell is a more exciting and enviable place to be than his present situation. He likes the dramatic imagery of the Bible but doesn't thoughtfully pursue its moral lessons, like most religious folk, Twain suggests.
Tom decides to pull out one of his treasures: a black beetle he keeps in a box. It lands in the aisle, where a stray poodle finds it. The beetle bites the poodle, which barks loudly and jumps into its owner's lap and then gets thrown it out the window. Tom is not alone in his delight—his fellow churchgoers laugh, too.
Tom can only remain well behaved for so long. The results of his mischief prove the same could be true of adults. In their shared delight at the antics of the beetle and the dog, a sense of community is created amongst all the villagers, ironically fulfilling their expectations of a church service.
Tom heads home in good spirits having discovered that variety can occur at church. He is mildly annoyed at having lost his beetle.
Tom's chief joy is avoiding the routine, and he feels a huge accomplishment in having shaken up the predictable course of a Sunday church service. Even so, he'll always be left wanting something outside his grasp. This insatiable appetite goes hand-in-hand with his youthful desire to avoid the routine.