As soon as Stanley realizes he and Zero may really make it to the Big Thumb, he begins to doubt that they will find water there, but he does not give up. He sets out uphill with Zero beside him. Soon the boys leave the barren lake behind. They walk past thorny weeds and begin to be tormented by bugs.
Stanley desperately wants a rest, but he is scared that he and Zero will not be able to start again if they stop. He resolves to keep going as long as Zero keeps going. To pass the time, he restarts the game of spelling words for Zero to sound out.
Suddenly, Zero vomits up all the sploosh he drank back at the boat. When he is finished, he gets up and tries to keep walking. Stanley encourages him, pointing out that there must be water nearby if there are plants and bugs. For a moment, Zero is thrilled—but then he passes out. Stanley cannot wake him up.
Stanley puts the shovel, the burlap sack, and the jars on the ground. He picks Zero up and keeps walking. He is not sure where he is getting the strength to go on, and he imagines that the Big Thumb is pulling him forward. He keeps climbing until the ground flattens out. Ahead of him, he sees a huge stone, and he loses hope. There is no way he can climb the stone, and even if he could, he does not see how could there be water at the top.
Unsure what else to do, Stanley keeps trying to get to the thumb. He continues until his strength fails and he collapses into the mud. Just as he is about to give up and let himself lose consciousness, he realizes something important:
You need water to make mud!
By now it is dark, and Stanley crawls forward through the mud. When he gets to ground that is very wet, he digs, and muddy water pools at the bottom of his hole. He drinks some, then he takes some to Zero and dribbles it into his mouth. Although Zero is unconscious, his tongue reaches out and licks up the water from his face. Stanley drags Zero closer to his well hole and sets about widening it. From time to time he pauses to scoop out water and feed it to his friend.
As he is digging, Stanley finds something smooth and round. It is far too dark so see, so it takes him a moment to realize it is an onion. He does not even bother to peel it; he just bites in. After he eats half, he gives the other half to Zero. By now Zero is awake enough to ask what it is. “A hot fudge sundae,” Stanley says.