Another Herod, not the one who ordered the killing of all the babies and subsequently died before any of them could be a threat to his rule back in chapter 2, thinks Jesus is the reincarnated John the Baptist, who was in prison back in chapter 11 but has apparently died off-screen.
We get the story in flashback. John was in prison not for baptising people, as you might think, but for telling the king's brother that his marriage was illegitimate. Herod wasn't planning to kill him, fearing riots, but then his niece danced so nicely at his birthday party that he let her make one wish. Her mother had coached her to say Give me here John Baptist's head in a charger. (v. 8) Which must have really sucked, because what she probably wanted was a pony and instead she gets a bloody head in a basket. Herod is reluctant, but he's even more reluctant to deal with the whining and sulking that comes with reneging on a promise to a teenage girl, so he does it. And she gets the head and takes it to her mother.
His followers take the body and bury it. Jesus hears about the death and goes out into the desert, because heaven forbid he let an opportunity to be dramatic go by. A bunch of people follow him and he starts healing. He gets so into it that soon it's evening and nobody's eaten anything all day. The disciples tell him to call it a day so everyone can have supper, but he says they have plenty of food. The disciples point out that five loaves and two fishes aren't going to cut it, as the crowd is up to 5000 people. Jesus tells them to bring the food to them, then looks up to heaven, then tells them to pass it out. In the end there are 12 baskets left over.
After dinner, Jesus finally does send the multitudes away, and tells his disciples to get on a ship and he'll meet them on the other side. Then he goes up a mountain and prays a bit. While he's there, a storm blows up on the sea, but he walks across it to the ship. The disciples are scared and think it's a spirit. He assures them that he isn't, but Peter says if he's really Jesus, he should ask him to come out onto the water as well. So Jesus does and of course Peter starts to doubt and sinks a bit, but Jesus lifts him up with an O thou of little faith, wherefore didst thou doubt? (v. 31) and he's fine. Don't try that one at home unless you can swim.
Anyway, a lot more people are converted.