The Man Who Was Thursday

I have just read C J Chesterton's The Man Who Was Thursday.An adventure story. A strange and surreal tale.I enjoyed the London setting. I liked the descriptions of shadowy figures in the fog and the fast pace of the writing .Nevertheless, what was the story about ?.Personally I have no idea.Can anyone shed some light on this mystery?.

Hi Priene
Well then. The consensus so far is ,the story is a bad dream.