The narrator begins the story by explaining that a friend of his back East has asked him to check in on an acquaintance, Rev. Leonidas W. Smiley. To do so, the narrator seeks out an older man named Simon Wheeler, and the rest of the story is the result of that visit. The narrator notes that he suspects Leonidas W. Smiley doesn’t really exist. He speculates that his friend knows the name will remind Wheeler of a man named Jim Smiley, and that Wheeler will launch into a long story about him. That is exactly what happens.

The narrator finds Simon Wheeler sleeping by the stove in a tavern in Angel’s Camp, a mining town. After waking and greeting Wheeler, the narrator asks him about Leonidas W. Smiley. Wheeler then sits the narrator down in the corner of the tavern and begins to speak. The narrator notes that during the entire account which follows, Wheeler hardly shows any emotion and never wavers from a singular gentle and monotonous tone of voice. According to the narrator, Wheeler doesn’t find anything funny whatsoever about the story he tells and in fact takes the matter extremely seriously and regards the men in the story as heroes. The narrator finds this absurd, but he does not interrupt Wheeler throughout his narrative.

Wheeler begins by describing a man named Jim Smiley, who came to Angel’s Camp in the winter of 1849 or spring of 1850. The interesting thing about Jim Smiley is that he would make a bet with anybody about anything. If a person was reluctant to take the bet, Smiley would switch sides just to entice them. Smiley loved to bet because he was very lucky and would almost always win. He especially loved to bet on animals, including horse races and dog-, cat-, and even chicken fights. But he would bet on unconventional and unusual things, too. He might bet on which bird among two would be the first to fly off a wire and which speaker at the town meeting was best at speaking. He would bet on where a random straddle-bug was going and how long it would take for it to get there and then follow the bug to Mexico so he could find out. One time Parson Walker’s wife was sick, and it was expected she may die. When she showed improvement and it looked like she may live, Jim Smiley told Walker he’d bet that she’d die anyway.

To feed his gambling habit, Jim Smiley kept a series of animals that he would use to place bets. One of these was a sickly mare with a variety of ailments. Despite looking like a wreck and starting each race slowly, the mare would get a burst of energy at the end of a race and almost always come out the winner, if barely. Another was a dog that Smiley named Andrew Jackson, who did nothing but sit around looking lazy. However, whenever Smiley put him up to a fight and bet on him, Andrew Jackson would suddenly get tough and mean. He would even let the other dog bully him and beat him up so the bets against him would pile up. Then suddenly Andrew Jackson would grab the other dog’s hind leg with his jaw and clamp down and never let go, and he would win the fight. Smiley never lost a bet on Andrew Jackson until he fought a dog without any hind legs. When it was time to clamp down on the other dog’s leg, Andrew Jackson discovered that he didn’t have any and gave up the fight. The old dog looked at Jim Smiley with disappointment on his face, as if he were heartbroken, then limped away, laid down, and died.

Next Jim Smiley caught a frog and decided to train it. For three months, all Smiley did was teach the frog to jump. He taught the frog to jump so high he would do one or two somersaults in the air and land back on his feet. Smiley said the frog only needed education to be able to do anything. He named the frog Dan’l Webster and started teaching him to catch flies. Dan’l Webster got so good at catching flies that Smiley only need to say, “Flies, Dan'l, flies!” and the frog would leap up, grab a fly off the counter with his tongue, and land back on his feet on the floor again, looking modest. Dan’l Webster’s specialty was jumping from a sitting position, and he could go higher than any frog there ever was. Jim Smiley was proud of his frog and bet on him whenever he could. People who had traveled everywhere said Dan’l Webster was the best jumping frog they’d ever seen.

One day, Jim Smiley was sitting in the camp with a small lattice box containing Dan’l Webster when a stranger walked up and asked him what was inside. Smiley told the stranger it was a frog. The stranger examined the frog in the box and asked what it was good for. Smiley responded that the frog could outjump any frog in Calaveras County and that he would bet the stranger forty dollars on it. The stranger said he didn’t see anything special about the frog, and he didn’t have a frog himself, but would take the bet if he did. Smiley said he’d go and get a frog for the stranger, so the stranger agreed to the bet. Smiley handed the box to the stranger and went down to the swamp to catch a frog. While Smiley was away, the stranger picked up Dan’l Webster, opened his mouth, and filled his body with quail shot.

Jim Smiley returned with a frog from the swamp and put the two side by side, ready for the jumping contest. Smiley then counted to three and the two men touched their respective frogs from behind to urge them to jump. The new frog jumped forward. Dan’l Webster, however, only gave a heave like he was trying to jump but couldn’t budge. Smiley was surprised and confused, but he paid the stranger the forty dollars as agreed. As the stranger walked away, he again said aloud that he didn’t see anything special about that frog. Smiley stood looking at Dan’l Webster for a while, wondering what was wrong with him. He noticed the frog did look a little baggy. He picked up the frog and was surprised to find that Dan’l Webster felt like he weighed five pounds! He then turned the frog upside down, causing Dan’l Webster to belch out all the quail shot inside him. Smiley suddenly understood what had happened and was angry. He went looking for the stranger but never found him.

At this point, Simon Wheeler hears his name called from outside and stops his story about Jim Smiley. He tells the narrator to sit still while he goes outside to check why he’s wanted. However, the narrator has had enough, and knowing he isn’t going to get any information about Rev. Leonidas W. Smiley, he starts to leave. As he reaches the door, Wheeler is just on his way back inside. Wheeler immediately starts in again with another story about Jim Smiley, this time about Smiley and a one-eyed cow with a stump of a tail like a banana. But the narrator, annoyed, interrupts Wheeler to tell him he doesn’t want to hear any more about Jim Smiley, and he leaves.