King Neb is dead. Long live the king! And now his son (or most likely not his son) Belshazzar is having a party. As the wine flows, he decides it's a good idea to get the gold and silver vessels from the sacked temple in Jerusalem so he can reenact every photo of the Stanley Cup ever.
Bad idea. A mysterious, detached hand appears and starts writing on the wall. Unfortunately, the language isn't Babylonian, so nobody can read it. Meaning it could say anything at all. The queen suggests that maybe Danny could be of service here, so the king sends for him. Danny basically tells him what you'd expect to hear: drinking out of the holy vessels was a big no-no and now he's going to die ignominiously and his kingdom will be divided. Rather than get a second opinion, Shazzar rewards him with a promotion to third in command. Then he dies and Darius takes over.
Daniel is the Tracy Flick of the Babylonian administration, and the other bureaucrats are the Mr McAllisters, trying desperately to find something wrong with him so they can kick him out. Of course they can't, so they draft a law saying anyone who petitions anyone but the king for something in the next 30 days will be thrown into the lions' den. The king happily signs the decree, because in the bible all kings are easily-manipulated fools.
Of course Daniel immediately makes a point of praying three times a day with all the windows open because he's incredibly irritating. And of course the other administrators catch him at it. They tattle to the king, who reluctantly throws him into the lions' den, because again, as the king, he has no power to change the law. As he's shutting the door, the king asks Danny if he really thinks his god will protect him. Danny assures him that he will. Note how few Christians today are willing to take the same leap of faith.
Of course Danny survives the night, and that's where most people think this tale ends. But it doesn't. Instead the other senior officials are gathered up, along with their wives and children, and thrown into the pit, where they are not as lucky as our hero. Then Darius issues another decree, this time that everybody has to worship god.