Zero grows strong enough to help dig the water hole. He makes it about six feet deep and puts rocks on the bottom to make the water cleaner, and then declares that it's the last hole he'll ever dig. Stanley knows they need to return to Camp Green Lake at some point. There's nothing but desert for miles. Zero wonders out loud if there's a hole in the top of the thumb and that's where the water is coming from, noting that water doesn't run uphill. Stanley realizes that the onion smell doesn't bother him anymore and he can't really taste them anymore either.
The realization that he's acclimated to the onion smell suggests again, as it did with Barf Bag's cot, that Stanley is capable of adapting to all manner of situations, not all of them positive. When Zero suggests the water must be in the thumb or running uphill, it draws a parallel between this stream and the Latvian stream of Madame Zeroni. This in turn implies that this stream, like that one, has magical powers.
Two nights later, Stanley happily stares at the stars. He thinks that he has no real reason to be happy and wonders if he's going to die. He realizes he's never been truly happy, but now he likes who he is. He watches Zero's breath blow a flower petal around and thinks that Zero had only been at Camp Green Lake a month or so more than Stanley. He thinks that even though Zero is right that neither of them would be here if he'd kept the shoes, Stanley is glad that Zero abandoned the shoes and they fell on him. He remembers how he thought that destiny struck him and thinks that it must've been true.
Stanley's happiness and satisfaction at the way things have worked out shows that he too will get to experience some of the satisfaction of the way that destiny works within the plot, even without knowing all the exact pieces. This suggests that, at its heart, the idea of destiny allows people to make more sense of their world and feel more secure in the way things progress in their lives.
Stanley wonders if he and Zero could possibly sneak past the camp and follow the road back to civilization. He reasons that nobody at Camp Green Lake is looking for them at this point. He dreams about living as a fugitive and getting a new identity, and he realizes it's crazy but also thinks that it'd be easier if he and Zero could find Kissin' Kate Barlow's treasure to fund their adventure. He wakes Zero up and asks if he wants to dig one more hole.
Given the way that Stanley's journey has mirrored Elya's thus far (and especially since he's now uncharacteristically happy), it suggests that it's actually part of Stanley and Zero's destiny to dig up Kate Barlow's treasure. It also implies that by doing so, they'll somehow atone for Sam's murder.