Read the excerpt from The Strange Case of Dr. Jekyll and Mr. Hyde. "You stay too much indoors,” said the lawyer. "You should be out, whipping up the circulation like Mr. Enfield and me. (This is my cousin—Mr. Enfield—Dr. Jekyll.) Come now; get your hat and take a quick turn with us.” "You are very good,” sighed the other. "I should like to very much; but no, no, no, it is quite impossible; I dare not. But indeed, Utterson, I am very glad to see you; this is really a great pleasure; I would ask you and Mr. Enfield up, but the place is really not fit.” How does this passage develop the theme "Secrets isolate people from those around them”?