This is a fascinating chapter as it gives us a lot of hints at the way things may go in the north. Readers may remember that Stannis' army is hunkered down in the snow, there's been a terrible blizzard, and they've taken shelter at an abandoned village in the woods. The Boltons control Winterfell and are sending some of their forces out to attack Stannis, although it's mostly Freys and Manderlys going out- two factions that have been at each others' throats inside Winterfell. Roose Bolton is probably thinking he's glad to be rid of them and hoping for high casualties on both sides. Also, Theon is newly arrived, having been captured after escaping Winterfell with Jeyne Poole, who was being passed off as Arya Stark to marry Ramsay.
Theon is now a prisoner, hanging in a tower as Stannis takes audience with various and sundry persons. Conditions are terrible as snow blows in every time the door is opened, and Theon reflects that knights and visitors have been coming to see Stannis all night. The first visitor we see is Tycho Nestoris, the banker from Braavos, who is finishing up negotiations with Stannis for a loan. Stannis sends Tycho back to Braavos by way of Castle Black, and assigns one of his knights- Justin Massey- to escort him. Further, Massey is to sail to Braavos with the banker and buy ships and sellswords there- at least twenty thousand men- and send them back to Stannis.
Stannis also instructs Massey to seek out the Golden Company if possible, and hire them if they're not under contract (little does he know they're already coming ashore on Westeros).
After the banker departs Stannis confronts a maester who sent birds to Winterfell to alert them of Stannis' location. After ferreting out the maester's lies he meets with Karstark and his son- both of whom have also betrayed Stannis by conspiring with the Boltons- and Stannis informs them they will be executed. We're seeing here Stannis reacting to those who have wronged him- and by having Theon strung up behind him as he takes audience, I suppose he's sending a message that way too!
His final meeting is with Asha, the sister of Theon. Asha was captured in an earlier battle and Stannis is mulling what to do with her. She tells Stannis that if he's going to kill Theon, he should do it as Ned Stark would do it- himself. Furthermore, there's a weirwood tree in the nearby abandoned village and she tells the king to give Theon to the old gods. At that point the ravens in the room go berserk, calling out Theon's name and saying "tree, tree."
I think the implication here is that Bran and/or Bloodraven are warging the birds and observing events. Why else call to Theon? He thinks too about how the heart tree at Winterfell spoke his name, before he got away. Some other tidbits here lend credence to the theory that Stannis has a trap set for Bolton. We learn that "Crowfood" Umber has dug pits outside the walls of Winterfell- concealed by the raging blizzard- and Frey forces rode forth and fell in, including Aenys Frey who broke his neck.