The first appearance of John the Baptist. It's not promising. He comes out of the wilderness, wearing a camel-hair dress and a leather belt, shrieking about how he eats locusts and honey and urging people to repent now, because the day of the lord is nigh. Honestly, le plus ça change, le plus c'est la même chose, man.
But actually, something has changed, because unlike in the days of the Old Testament prophets, when everyone just ignored the weird guy telling you you were going to die, people are convinced by his message and follow him over to the Jordan River to get baptized. But not the Pharisees or the Sadducees, who he calls vipers (v. 7). He tells them they can prove their dedication to god by producing fruit. Failure to do so will result in death by fire. I always thought this was the hippy, non-violent bit of the bible. This is only chapter 3 and we're already discussing mass slaughter. They also need to stop thinking they're fine because they're also descendants of Abraham. So much for the credo of tolerance.
John also tells them that he baptizes with water, but that the coming saviour will baptize with fire and the Holy Ghost. There are a lot of other references to burning. For a book that's supposed to be about peace and brotherhood.
One day, Jesus comes along to be baptized, because it's what all the cool kids are doing. But John refuses, pointing out that he's actually the one who should be baptized here. Jesus says that rules are rules, so John just shrugs and does it.
When Jesus reemerges, he sees a window in the clouds that looks straight into heaven, where he sees god, who is pleased.