Okay, this is capital-letters Science Fiction (with a side of horror). Did turning invisible turn the man mad, or was he insane to begin with? I think at first merely selfish, compounded into arrogance over years of academia, culminating in the murderous, larcenous delusions of grandeur you see. I find it hilarious the unnamed American carrying a pistol was such a useful character. Griffin made me think of Uncle Andrew in "The Magician's Nephew".