"All I could think clearly was that the thing had to be carried through; the fixed idea still ruled me. And soon, for the money I had was almost exhausted." (20.33)
Griffin is clearly obsessed with the idea of becoming invisible (that's the "fixed idea" that rules him.) That's sort of classic mad scientist stuff: an isolated scientist obsessed by a crazy idea. But he has another major problem: he doesn't have enough money to experiment safely. What would this story be like if wealth weren't an issue?
"I turned down one of the roads leading from Gower Street to Tottenham Court Road, and found myself outside Omniums, the big establishment where everything is to be bought—you know the place: meat, grocery, linen, furniture, clothing, oil paintings even—a huge meandering collection of shops rather than a shop." (22.3)
Omniums is a department store, which is kind of a new thing in England. (They were actually new in the nineteenth century. That's why Griffin has to describe it a little, because some people might not really know what it's like.) It's interesting to us that a man who is on the cutting edge of science is also on the cutting edge of commerce here. (By "commerce" we mean "shoplifting.")
"But if you betray me," he said, "if you fail to do as I direct you—" (9.71)
The Invisible Man is not a very trusting individual. As soon as he gets a partner, he starts talking about betrayal. It's almost as if the Invisible Man <em>expects</em> people to turn against him. Why might this be?