Jon is inspecting supplies beneath Castle Black, and we learn that there are tunnels all over underneath the place, called wormways. It's how the Nights Watch get around quickly in the winter when the snows are high. The situation is not good (this is Game of Thrones, what's new?) - they have a lot of food stored but Bowen Marsh says they will go through it fast, especially with Stannis' people.
Afterward Jon is summoned before Stannis, and when he gets there he sees that Massey and Horpe have returned (they're the two that Stannis sent south on some mission). Stannis asks him about Mors Umber- he tells him that Horpe and Massey want Winterfell, and Massey wants Val as well. Stannis is more inclined to give Winterfell to Karstark, after he offers it to Jon again and Jon refuses again.
Jon advises Stannis to go to the mountain clans and ask for their support, and then to march on Deepwood Motte. He says the clans, Flint, Wull, Norrey, Liddle will fight for him.
Jon is skirting the edge of neutrality by offering Stannis counsel on how best to proceed in the north. Can't blame him though, as the alternative is bleak.
The Shy Maid is still heading downriver and they pass another boat, from which they learn that Volantis is at war and that Nyessos and Malaquo are for it. Griff remarks that Illyrio paid Nyessos for his support and they should own him, but Tyrion thinks that the Volantene might have reason to fear the dragon. An argument breaks out and Tyrion reveals that he knows who Young Griff is-and Griff as well.
COMMENTARY: The big news here of course is the revelation about who Griff and Young Griff are.