How does The Purple Cloud develop the theme of Isolation and Madness?

The Purple Cloud by M. P. Shiel develops Isolation and Madness across the chapters the companion marks for this theme.

The protagonist's solitary survival after the destruction of humanity leads to a deteriorating memory, internal voices, and a struggle with sanity, highlighting the psychological toll of absolute loneliness.

Jeffson's solitary wanderings in a deserted London and his growing whimsical imperiousness hint at his descent into madness.