In Christopher Booker's analysis of the "Rebirth" narrative, the main character has to fall under the sway of a dark power, and it is tough to find a darker power in The Jungle than capitalism itself. Under the competitive rules of capitalism (according to Upton Sinclair), you have to struggle for every single penny that you earn. Meanwhile, the system is stacked against you by rich men who already monopolize all the money, power, and resources available. When Jurgis arrives in the United States, he believes (naively) that he is going to strike it rich. However, there is already foreshadowing that Jurgis's hopes are going to be for nothing: the family can't even make it to the city of Chicago without being cheated multiple times by swindlers and custom agents. They really are not prepared for the cutthroat business world of Chicago's Packingtown.
Of course, it takes some time for Jurgis to realize how out of his depth he is in Chicago. At first, he turns up at a meatpacking plant and gets a job right away. He is young and strong, and he makes a pretty decent wage. Jokubas Szedvilas arranges work for Jonas, Marija finds a job on her own, and even Dede Antanas manages to rustle up work. So it seems like everything is going to work out great. They just have to find a house to settle in, Jurgis can marry Ona, and all will be well – right?
Once Jurgis and his family buy a house, they are totally trapped. They tried to get ahead in this capitalist system, they got swindled, and it's game over. They don't see that they are ruined right away, but it's like air leaking out of a balloon: eventually, the balloon's going to go flat, no matter how hard you try to stop the holes. Once they have to make a high monthly payment beyond their means, there is no room for accident. When Jurgis injures his leg, Stanislovas and Ona have to go into the workplace. When Antanas dies and Jonas disappears, Vilimas, Nikolajus, Teta Elzbieta, and Kotrina all eventually have to get jobs. Once Jurgis gets thrown in prison and Ona dies, the jig is up: Jurgis's family has gambled by entering moving to the United States, and they have totally lost. They have entered into a period of ruin.
Once Jurgis's hopes of a rosy future with Ona and a brood of children fade away, he is lost. He leaves Teta Elzbieta and Marija behind and becomes a wanderer. He returns to Chicago as a criminal. Having become thoroughly jaded, he tries to make the underworld of Chicago work for him. He seems to be succeeding for a while before he ends up penniless on the streets yet again. Jurgis has no future left to him; he really just seems to be drifting from place to place waiting to see what turns up.
After wandering in darkness for over a year, Jurgis finds hope for the future from an utterly unlikely place. He stumbles into a Socialist Party meeting where he hears a message for working men to organize for change of the American system. Once Jurgis becomes a socialist, he stops worrying about his own future so much. Instead, he starts dreaming about a future for all the workingmen of the world. Even if Jurgis's family life is still a shambles, he now feels part of a new family: the Socialist Party. Jurgis has been reborn as a socialist, and he will never feel lost or lonely again.