In this famous short story by Chekhov, a lawyer and a banker agree to a bet. Emerging from an argument over whether the death penalty is more immoral than life imprisonment, the lawyer claims he would be able to withstand fifteen years in confinement, while the banker agrees to pay him a sum of two million rubles should he succeed. The story is set at the very end of this fifteen-year timeframe.
Situational irony always involves a kind of twist or reversal of expectations, and this can be seen in both the banker's and lawyer's present situation. As we find out, in the fifteen years since the two had made their agreement, the banker's fortunes have been shaken dramatically. If the bet had come due fifteen years earlier, he would have been able to pay the wager with little real difficulty (this is part of why he thought so little of it at the time), but now, when the wager actually is set to come due, its impact on his finances is set to become ruinous. For the banker, this is an ironic turn of fortune.
Meanwhile, there is the lawyer, who has spent fifteen years in confinement, initially expecting to receive two million rubles for his sacrifice. However, he emerges from these fifteen years in seclusion greatly disillusioned on the materialism of Russian society, with that prize of two million rubles having lost all value. Thus, now at the very end of this fifteen-year confinement, he intends to resign the wager, exiting only minutes before the deadline has been reached.