What Spirits? What Prison? Preached What?

In one of the most difficult texts of the New Testament, Peter tells us that Jesus went and preached to the spirits in prison who were disobedient in Noah's day. Who are these spirits? What prison are they in? What did He preach to them? When did He preach to them? What did they do (or not do) in Noah's day? There are many possible answers to these questions. We will examine the difficult portions of this passage and examine several of the proposed answers.