In this Chapter we have a new king sitting on the throne in Babylon who makes the most serious mistake he could make.  God sends him a message that scares him.  Daniel is brought out of retirement to come and interpret the sign from God.  When he does, God sets his judgement in to action and that king's reign is ended.  This is the Biblical account that gives us our cliche, "Can't you see the handwritting on the wall?"