What does the invisible man seem on the verge of? What would he be terrified of?

The invisible man is on the verge of mental collapse, he seems to have gone completely crazy. He would be terrified of being discovered.

Possibly the Invisible Man's original intention was simply to cover Marvel's retreat with the clothes and books. But his temper, at no time very good, seems to have gone completely at some chance blow, and forthwith he set to smiting and overthrowing, for the mere satisfaction of hurting.