The Invisible Man
How we cite our quotes:
"[...] a footprint as isolated and incomprehensible to them as Crusoe's solitary discovery." (21.15)
You know how in alien invasion movies, someone always says, "we're not alone"? We imagine the London urchins might feel something equally strange (and awe-inspiring) when they see this footprint that they can't explain. (Check out the "Allusions" for more on the Robinson Crusoe.)
"What was I doing? Why was I always alone and secretive? Was it legal? Was it dangerous?" (20.37)
Here we have Griffin talking about his landlord in London. Or rather, it's more like Griffin speaking for the landlord, who is worried that Griffin is up to no good. And the landlord's evidence that Griffin is bad news? He's always alone.
"By this time I knew he was alone in the house, and so I made no more ado, but knocked him on the head." (23.20)
Sometimes being alone is associated with being vulnerable. Here Griffin tells Kemp how he took out the costume-shop owner: as soon as Griffin realizes the guy is alone, bam, he knocks him out. (You'd almost imagine that Griffin would empathize with people who are alone like him, but no – he doesn't seem to care about anyone.)