Moving back in time slightly, we get a glimpse into what Sotillo had been up to leading to Hirsch's death and his exit from the Custom House.
Earlier that day, an emissary from Fuentes had come to talk to Sotillo. The emissary had intended to get Sotillo to come meet with Pedrito.
However, because the prospect of meeting Pedrito terrified Sotillo—and because he wanted to be free to go looking for the silver he assumed was still lying around—he pretended to be too sick to receive Fuentes's man. He promised he would be better the next day—and, until then, hoped that the envoy would do him a solid and stop by the Goulds to tell the doctor he was needed at the Custom House.
He continued to be anxious for the doctor to return—not for his health, of course, but to get more info on the "treasure." Then he realized that Hirsch, who had remained his prisoner, could be pressed for those same details.
He tortured Hirsch, but didn't get any additional information (naturally, since Hirsch was telling the truth… as far as he knew).
During the torture, Hirsch spat in his face. In response, Sotillo impulsively shot him.
He immediately regretted the decision, since he believed Hirsch had information he needed—plus, if his men knew Hirsch had died without providing the location of the treasure, he would be in deep trouble.
So, when his men ran in and asked what was up, he lied and said Hirsch had confessed, which is why he decided to kill him. He then ordered his men to move out of the Custom House and burn it on their way out.
The narration then flashes forward to the doctor and Nostromo talking in the Custom House later, after they have found Hirsch's body. The doctor is very perplexed by the fact that Hirsch was shot.
The doctor is also thinking about how crucial Nostromo will be to the success of his own plans and interests—which included getting Barrios back to Sulaco.
He suggests that Nostromo go to the Casa Viola to hide out before going to Cayta. Nostromo struggles to figure out the best course of action that will ensure both glory and security for him.
Nostromo indicates he is open to going to Cayta as long as the chief engineer can be convinced to help get him there.
While they are chatting, the doctor casually mentions that he will tell Sotillo the treasure has been buried on the Great Isabel (since he has to tell him something to keep him busy). Naturally, Nostromo is horrified that the doctor has accidentally chosen the real location of the silver. Without telling the doctor anything, Nostromo convinces him to tell Sotillo it was sunk somewhere in the harbor that could be searched easily. The doctor agrees.
Then, Nostromo decides he has to go into town to talk to the Goulds, but the doctor convinces him to just go straight to the Violas to keep him out of sight.
When Nostromo enters, he finds Giorgio sitting in the dark. They chat, and Nostromo demands a snack.