I have always said the bible lacks enough good dragon stories. This one was also cut off from the end of Daniel, though it doesn't specify whether that was for not being in Hebrew or some other reason.
Anyway, we start off with Daniel and King Astyages of Persia having a conversation. We also learn that the Babylonians have a god named Bel, to whom they sacrifice 12 heaping portions of flour, 40 sheep, and 6 wine casks. The king also worships Bel, but Daniel has his own god. The main thrust of this conversation then is, why doesn't Daniel worship Bel? And of course Daniel has to be as obnoxious as possible and answer Because I may not worship idols made with hands, but the living god, who hath created the heaven and the earth, and hath sovereignty over all flesh (v. 5). Which of course immediately riles up the king, who asks if Daniel doesn't believe Bel is a living god, given how much he eats?
Somehow, Daniel manages to get even more obnoxious by smiling and replying that his host's god is just brass and clay and doesn't really eat. The king calls his chief priests over and tells them to figure out where all the flour, wheat and wine is going on pain of death, either theirs or Daniel's. I mean, I'm not in favour of the death penalty for blasphemy or anything, but I'm not sure how I feel about the death penalty for rude houseguests named Daniel. Of course, Daniel is not fazed by the idea of death.
We find out that there are seventy priests to Bel and they all have wives and children. They all go to the temple with the king and Daniel. The priests explain that they're going to go out, and the king should set out the holy meal, then leave and seal the door. In the morning, they'll know who is going to die. And of course the priests are confident because they have a door in the floor that they use to go in and eat every night.
So they king sets out the meal. While he's doing that, Daniel covers the floor in ashes. Then they leave. The priests come in with their families and eat their meal.
In the morning, Daniel and the king go back to the temple. Daniel agrees that the doors are still sealed. The king opens the door and shouts praise to Bel. But Daniel, continuing his campaign to be the worst guest in recorded history, laughs and asks whose footprints are in the ashes. The king notes that they are the prints of men, women and children, which proves nothing, but anyway, he goes to his priests, who confess to eating all the nightly food. And of course Astyages puts them and their wives and children to death. Then he gives the temple to Daniel, who destroys it.
The Babylonians also worship a dragon, because smart people will hedge their bets. The king asks Daniel if the dragon is also made of brass. Daniel says no again and offers to slay the dragon without any weapons. So Daniel makes an incendiary device (a weapon, no?) and puts it in the dragon's mouth. The dragon explodes and Daniel makes fun of the Babylonians and their false gods.
Now, needless to say the people start hearing about this indecorous foreigner who is apparently turning the king into a Jew and start feeling rebellious. They go to the king and demand Daniel or they'll overthrow him. And the king, being more of a politician than a theologian, hands him over. He's thrown into a den with seven hungry lions.
There is a certain prophet named Habbacuc who has made some soup and bread and is carrying it to the field to feed the threshers, but an angel visits him and tells him to take the food to Daniel instead. Habbacuc replies that he doesn't know where that particular lions' den is, so the angel picks him up by the hair and carries him there. He offers the dinner to Daniel, who eats it. A week later, the king comes down and finds Daniel safe and sound, so he throws the people in the den instead. Charming. I can see why people are so taken with this book.