I initially wanted to watch this film to see Humphrey Bogart in a Western type movie. I am really impressed by how great this movie was.
Fred Dobbs (Bogart) meets Bob Curtain (Tim Holt) in a Mexican town where both Americans are begging for money and looking for work. They both end up working for a man named McCormick in the building industry in Mexico. McCormick has many men working for them and promises to pay them $8 US dollars a day once they are back in Tampico. Once they get back, McCormick tells the men that the person that is supposed to meet them with the money is not there. He tells them that he will go to his office and bring the money back to the ferry. Dobbs and Curtain do not trust McCormick and ask to go with him, McCormick gives them some money and tells them to meet him at a bar at 3. Mccormick never shows up and the locals inform them of the scam the McCormick runs on desperate men to get free labor. With hardly any money left after drinking at the bar, Dobbs and Curtain head to a run down rooming house where they meet Howard (Walter Houston). Howard is talking about mining for gold in Sierra Madre, but warns the men that gold can turn good men into bad men. Dobbs and Curtain, after leaving the rooming house, talk about mining for gold and bringing Howard in on it. Dobbs fears that they would have to carry the older man because he would not be physically fit, Curtain said don't under estimate him just for being old. At this point Dobbs asks Curtain if he believes what the old man said about gold turning good guys into bad with greed, and they both decide that they would not be effected by gold and wealth in that way.
The three men make the journey to the mountain and start the mining. The more gold that they mine, the less they trust one another, especially Dobbs. They decided to divide the gold up nightly with each man being responsible for his own share. They are all leery of the others. While they are mining in a cave, the cave collapses and traps Dobbs inside, Curtain has the choice to go in and get him or leave him there, he decides to rescue him. This does not stop Dobbs from feeling like Curtain was going to kill him and steal his gold. On one of the trips into town curtain is tailed by another American, Cody (Bruce Bennett),that wants to mine for gold. Coy does not want a share of what was mined but what would be mined. The three men decide to kill him instead of sharing the wealth or risk him turning them in. Cody is saved because of bandits, but is killed by the bandits. Curtain wants to give a fourth of the gold to Cody's wife and son, Howard agrees, and Dobbs is totally against the idea. The three decide to close up the mountain and head back into Durango to exchange the gold for cash. Along the way, Indians find them and ask for help for a boy that has nearly drowned by was unresponsive. Howard goes along with them and saves the boy. The Indians come back to repay Howard, where Dobbs does not want to delay going into town and wants to kill the Indians. Howard tells Dobbs and Curtain to take his share of the gold, head to Durango and he would meet them there. Along the way Dobbs gets more and more delusional and decides he wants to take Howards share. Curtain stands up for Howard, which makes Dobbs believe that Curtain is going to kill him. Dobbs shots curtain, and leaves him for dead, and takes off with all the gold. Curtain was not dead, but was found by the Indians and reunited with Howard. Together they go after Dobbs to retrieve their share of the gold. Once they get into Durango, they find out that Dobbs was killed by bandits, and later discover that they gold was lost because the bandits thought it was dirt. Howard and Curtain find humor in the situation. Howard goes back with the Indians as their Medicine Man, and Curtain decides to go to Dallas, where Cody's widow and child are.
There is a strong moral in this story, that greed can and does change people, and karma is always there. Dobbs shot Curtain for greed and money, and ends up being killed and stripped of his shoes and clothes by bandits in the middle of nowhere.