Victarion is on his way to find Dany. He takes loads of ships but with the storms, only a proportion of them make the rendezvous. He waits but he can't wait too long, he wants to get to Dany before the Volantenes attack her, rumour of which he's heard in some port or other. His mission is to bring Dany back so she can marry Euron, but he plans to take her for himself. I'm pretty sure they've both got delusions of grandeur except that she can probably make use of the ships. And if he takes the Volantenes from the rear as he plans it will be pretty handy.
He's got a gammy hand and his maester isn't very good at curing it. Luckily, who should show up but Moqorro, the red priest from Tyrion's ship. Seems he didn't fail to predict his own death after all. Moqorro does some magic and presumably cures Victarion's hand because the maester gets thrown overboard.
I think this is symbolic of the decline of science and the rise of magic, which has been hinted at before, and is the opposite of the situation in The Lord of the Rings. Or perhaps it is an eternal struggle between the two. Perhaps instead of a good god and an evil god, as Melisandre would have it, there are the gods and there is science. I don't think the maesters are entirely good, though. I think that bitter old lady at Winterfell might well be onto something.
