context: In 1925 in the Mexican oil-town of Tampico, Dobbs (Humphrey Bogart) and Curtin (Tim Holt), two Americans cheated out of promised wages and down on their luck, meet old prospector Howard (Walter Huston). When Dobbs wins a small jackpot in the lottery, they have the bankroll to finance a gold prospecting journey to the remote Sierra Madre mountains.
  They ride a train into the hinterlands, surviving a bandit attack en route. In the desert, Howard proves to be the toughest and most knowledgeable; he is the one to discover the gold they seek. A mine is dug, and much gold is extracted. Greed soon sets in, and Dobbs begins to lose both his trust and his sanity, lusting to possess the entire treasure. Dobbs is also unreasonably afraid that he will be killed by his partners.
  A fourth American named James Cody (Bruce Bennett) appears, which sets up a debate about what to do with the new stranger. Rather than give him a share of the future production of the mine, the men decide to kill Cody. Just as the three confront him with pistols and prepare to kill him, the bandits reappear, crudely pretending to be Federales. After a tense vocal exchange regarding proof, a gunfight with the bandits ensues, in which Cody is killed, a real troop of Federales appears and chases the bandits away.
  Howard is called away to assist local villagers to save the life of a seriously ill little boy. When the boy recovers, the next day, the villagers insist that Howard return to the village to be honored. However, he leaves his goods with Dobbs and Curtin. Dobbs, whose paranoia continues, and Curtin constantly argue, until one night when Curtin falls asleep, Dobbs holds him at gunpoint, takes him behind the camp, shoots him, grabs all three shares of the gold, and leaves him for dead. However, the wounded Curtin survives and manages to crawl away during the night.
  Nearly dying of thirst, Dobbs is ambushed and killed at a waterhole by the same bandits they encountered earlier at the mine. In their ignorance, the bandits believe Dobbs' bags of unrefined gold are merely filled with sand, and they scatter the gold to the winds. Curtin is discovered by indios and taken to Howard's village, where he recovers.
  The bandits try to sell the packing donkeys but a child (Robert Blake) recognizes the donkeys and Dobbs' clothes and reports them to the police. The bandits are captured, sentenced to death and forced to dig their own graves before being executed. Curtin and Howard miss witnessing the bandits' execution by Federales by only a few minutes as they arrive back in town, and learn that the gold is gone.
  While checking the area where the bandits dropped the gold, Howard and Curtin notice some empty sacks and surmise that the winds must have carried the gold away, back to the mountain from which it came. They accept the loss with equanimity, Howard proclaiming it a good joke and laughing while doing a little jig. They part ways, Howard returning to the indio village, where the natives have offered him a permanent home and position of honour, and Curtin returning home to the United States, where he will seek out the widow of Cody in the peach orchards of Texas.
question: What does curtin see?
answer: empty sacks