Jon and the wildlings ascend the wall. Only one team of climbers fall to their deaths. Once ladders are in place it's easier for everyone else. Ygritte reveals that the secret thing Mance Rayder was looking for was called the Horn of Winter, a.k.a the Horn of Jaramun, supposedly with the power to destroy the wall.
Oh, and digging up graves looking for this horn is what has made the Others reappear. This is not going to end well.
