At the beginning of "The Bet," a young lawyer voluntarily agrees to place himself in solitary confinement in order to prove that "it's better to live somehow than not to live at all." He wagers two million rubles with the banker that he can stay not just five years, which is the original bet, but fifteen years. He then enters this self-inflicted confinement.
During his first year of confinement, the lawyer plays piano and reads "books of a light character." As the years pass, he begins to study various subjects with increasing intensity, including languages, philosophy, the New Testament, the natural sciences, and medicine.
Hours away from completing his fifteen-year confinement, the lawyer writes a letter to explain that he doesn't plan to complete the bet. Instead, he plans to leave five minutes early, thereby forfeiting the entire amount. Through his studies, he has come to view the world much differently than he did when he made the bet.
He realizes that mankind is "proud and wise and beautiful," yet people fail to realize that death will eventually "wipe [them] from the face of the earth like the mice underground." All that they have worked to build and create will eventually be "burnt down" and destroyed. Mankind invests so much energy into the acquisition of wealth and status that they "take falsehood for truth and ugliness for beauty," failing to realize their own errors. He believes that humanity is "mad" and that they have traded "heaven for earth," placing their faith in the sinful ways of society rather than investing in things of eternal significance.
The lawyer ultimately rejects civilization because of all he has learned in confinement; he no longer desires the banker's money and instead wants the world to see his rejection as a condemnation of their values.
Ironically, the banker locks the lawyer's letter in a safe, never showing it to anyone. He is more concerned with his financial status than the truth, thereby proving how painfully accurate the lawyer's realizations are.