Several years before the beginning of this story, the narrator says, a giant mole appeared in a remote provincial village. The mole briefly attracted the attention of some locals at the time, and even some visitors from the surrounding area, but most people soon lost interest. The one man who did not was the elderly schoolmaster of the village, who took it upon himself to prove the mole’s existence to the wider scientific community. He published pamphlets and met with a scholar to drum up awareness of the mole, but his efforts were routinely ignored or derided.
Meanwhile, the narrator, living in a nearby city, has heard of the schoolmaster’s struggle and takes pity on him. He finds the schoolmaster’s rejection by the scholarly community to be unfair and makes it his mission to help the schoolmaster’s cause. The first step, the narrator decides, is to publish a pamphlet of his own that will defend the schoolmaster’s credibility. But the only attention the narrator seems to arouse is that of the schoolmaster, who becomes distracted by the appearance of an intervener in the mole episode and starts to grow suspicious of the narrator’s intentions—believing that the narrator wants to take credit for the mole’s discovery.
The schoolmaster’s jealousy deepens over the years, even as the men end up meeting each other on several occasions and trying to collaborate. Instead of collaborating, however, the schoolmaster spends his time complaining about the lack of public interest in the mole and blaming the narrator for his failed efforts to help. Simultaneously, the narrator describes the slow shift in his own interests: from a philanthropic urge to support the helpless teacher, toward an interest in the actual mole itself. He starts investigating the original appearance of the mole—interviewing witnesses and gathering so-called “evidence.” This shift in the narrator’s interest is viewed by the schoolmaster as a transgression on his territory. The schoolmaster’s jealousy deepens and his accusations grow more personal.
As an undisclosed number of years and pamphlets go by, the public still proves uninterested in the mole. The narrator reaches his breaking point when a jeer at the men’s efforts appears in the obscure back pages of an agricultural journal. The narrator decides to wash his hands of the affair and tries to recall all the copies of his pamphlet he had sent to various scholars. Just as the copies start to arrive, the schoolmaster comes to visit him in town over Christmas. Immediately, the schoolmaster launches into a diatribe on the agricultural journal’s notice, and an argument erupts between the two men.
In this argument, the men reveal the motives that have pushed them all along. The schoolmaster describes, in minute detail, the great fame and fortune that he hoped to achieve from his scientific discovery. The narrator, incredulous at the schoolmaster’s delusion, tries to talk some sense into him by positing a more realistic hypothetical outcome: the schoolmaster might have been recognized locally, but his discovery would have been absorbed into the broader scientific community and would cease to belong to him. In describing this possible outcome, the narrator reveals that his own motives for becoming involved with the mole episode—while once thought to be philanthropic in nature—have actually been unclear to him all along. The men conclude at a standoff; though the narrator plans to turn out the schoolmaster then and there, he cannot bring himself to do so.
