After swimming and sleeping hard, Nostromo wakes up a bit befuddled. However, he quickly gets with it and tries to formulate a plan.
He sneaks around for a bit and checks out the harbor, seeing that Sotillo's steamer is there.
As he is walking, headed for the Casa Viola, he sees a group of infantry marching off for the country. Hmm…
He decides to switch up his destination, heading instead toward the harbor. When he comes to the Custom House, which is lit up, he becomes curious about who is in there and decided to stop.
He discovers that someone has tried to light the stairs in the hall on fire; however, the flames have failed to catch.
While he is prowling around trying to figure out who is actually in the Custom House (he can see the shadow of someone upstairs), the doctor arrives. Thinking that he was expected by Sotillo and/or his guys, he heads up to the room with the lit windows while Nostromo waits.
The doctor then calls Nostromo in, assuring him it is safe for him to enter.
When Nostromo complies, he finds that the shadowy figure he'd been stalking within the lit room has been poor Hirsch swinging from the ceiling by a rope, having been tortured and then shot. Aww, poor dude.
The doctor tells Nostromo the story Hirsch told Sotillo, and Nostromo is relieved to learn Sotillo still thought the silver had sunk with the lighter.
The doctor also informs Nostromo of Teresa's death.
Then, they discuss the silver (mostly Sotillo's obsession with it). The doctor notes that Sotillo refuses to believe that it was lost and thinks Hirsch was lying. The doctor encourages that impression, prompting Nostromo to tell him he's dangerous (i.e., for endangering Hirsch through that lie).
The doctor is surprised that Nostromo would consider him dangerous. Privately, he thinks about how much he hates the subterfuge involved in manipulating Sotillo, but he remains determined to see the task through to the end, despite the personal dangers.