Before he got out of it again, the second reign of Napoleon, the Hundred Days of feverish agitation and supreme effort, passed away like a terrifying dream. The tragic year 1815, begun in the trouble and unrest of consciences, was ending in vengeful proscriptions.
Now, I've got problems with "the trouble and unrest of consciences". What exactly does the author want to say here? In what way can a conscience be troubled or in a state of unrest with regard to the context. Is it an idiomatic expression, or a straghtforward one (to those who can grasp it)?
Difficult to say precisely. Conrad's use of English can be very obscure. I think he is implying that the early months of 1815 - when Napoleon faced increasing opposition - was a time when the consciousness of people in Europe was that something had to be done about him. He is using the word in the sense of "awareness of right and wrong", and indicating that these people are in some confusion as to what to do.