Bran, Robb, Theon, and some guards go off on a ride: Bran's first ride with his special saddle.
Bran gets separated from the pack and suddenly four outlaws from the north come to attack him: the two men (Stiv and Wallen) are dressed in black, so they're probably deserters from the Night's Watch (and deserters get executed, as we know from chapter two); but the women (Hali and Osha) are wildlings, the people who live north of the Wall. Of course, that difference doesn't really matter when they're trying to take Bran hostage.
But Robb and the wolves and Theon save Bran (although Theon does take a chancy shot with his bow and arrow). Robb decides to take the surviving woman back to Winterfell for questioning, and this is how the Starks get a new servant out of Osha.