Pretty curious and thought-provoking.
Gavin's vision of his "parallel universe" shows the other side of the so called civilized man i.e. his evil counterpart. That's interesting. The author seems to visualize through the camera lens that which never surfaces if seen with the naked eye.
The more interesting thing is that David might not be able to see what Gavin has seen. He might see something which relates to his private self.
I don't know if I am right about my conjecture but that's how it strikes me.
So when Gavin sees the inherent evil in his lab and in himself, he is naturally shattered and that explains the bruised teary look I guess. Looks more symbolic than a mere horror centered story.

Language and the style of revealing the strange facts appeal to me.

Write on!