There is an unusual "change in the weather" at the always sunny, always hot Camp Green Lake (127). A storm starts brewing, and the resulting lightning lights up the edge of the lake basin, allowing Stanley to see that one of the distant mountains resembles a thumbs-up. He remembers that his great-grandfather found refuge on what he called "God's Thumb," and speculates that his great-grandfather may have been robbed by Kissin' Kate Barlow close to Camp Green Lake.
Zero is still digging part of Stanley's hole each day, so that Stanley has the energy to teach him how to read. The other boys resent this, and taunt Stanley endlessly for treating Zero like his slave.
The tension between the boys in Group D escalates until there is a scuffle in which Zigzag physically accosts Stanley. Mr. Pendanski urges Stanley to fight back, but Zigzag is more adept at fighting.
Zero eventually intercedes on Stanley's behalf, almost choking Zigzag to unconsciousness. The Warden is summoned. She and Mr. Pendanski mock Zero for not being able to read, and they say that Stanley must stop the reading lessons because it is making Zero more violent. Zero hits Mr. Pendanski across the face with a shovel and runs away into the desert.
Stanley is worried about Zero, who left without any water. The authority figures at the camp destroy all of Zero's records, noting that no one will come to look for Hector Zeroni - he is a friendless ward of the state.
Zero's spot in Group D is filled by a new campmate named Twitch, whose specialty is stealing cars. It is Stanley, though, who goes on a car-stealing spree soon after: he gets behind the wheel of Mr. Sir's truck when Mr. Sir is filling the boys' canteens, and tries to drive away. Stanley doesn't get very far; the car winds up in a hole.
Stanley sets off across the desert, hoping to find Zero. As he walks, he realizes the danger he is in: he has no water, no idea where he's going, and there are yellow-spotted lizards everywhere. Just before he decides to turn back, Stanley finds an overturned boat in the middle of the wasteland. A hand reaches out from under the boat: it is Zero.
The opening of Part Two clearly indicates to the reader that the (already quite gritty) novel is going to take a turn for the darker. The pathetic fallacy of the brewing storm symbolizes the tension and conflict that will follow. The lightning in Chapter 29 has further symbolic resonance: it is like a metaphorical light bulb that goes off in Stanley's head, allowing him to connect the distant form of a thumb-shaped mountain with the ramblings of his insane great-grandfather.
The idea of miracles is developed somewhat at the opening of this section, with several religious references littering the text. When rain becomes a possibility, X-Ray jokes that it will rain for "[f]orty days and forty nights," and the boys "better start building... an ark" like Noah did in the Bible (128). In the same chapter, Stanley remembers that in family myth, his great-grandfather married his great-grandmother because he thought she "was an angel," and alongside this, we have more references to "God's thumb" (129). This cryptic remark of Stanley's great-grandfather will prove to be a miraculous oasis in the desert, where Stanley and Zero will manage to avoid death by thirst, starvation, and exposure. It is interesting that Christian religion and folk-magic exist side-by-side in this novel, but they are both linked by the theme of the fantastic or supernatural.