What is the climax of the short story "Misery"?

The climax of a story is its point of highest tension or crisis. All through the story, Iona, a poor man who drives a horse and cab in freezing, snowy Russian weather, wants to tell someone of his misery. His son died a week ago, and he is heartbroken. He wants to unburden himself and talk about the hospital, the death, the funeral, and his strong sense that it is he who should have died and his son who should have lived. He tries to talk to the few people who take his cab, but they are not interested in the least. He wonders if any one of the thousands of people in the city would listen to him, and he feels very alone. Finally, he goes back to the yard where the cabmen congregate, hoping he can talk to someone:

He wants to talk of it properly, with deliberation. . . . He wants to tell how his son was taken ill, how he suffered, what he said before he died, how he died . . .

But even here, there is nobody willing to listen. Finally, full of his pent-up misery, Iona goes to see his horse in her stall. At this point his need to tell reaches the breaking point. This is the climax, and he relieves his anxiety by telling his horse all about his son's death.