And, of course, he returns with Jon when Sam, Grenn, and Pyp convince him to honour his Night's Watch vows rather than abandoning them for his family.

When Mormont later addresses Jon about how the REAL war is with the dead, not for the Iron Throne (sound familiar?), he says, "I want you and your wolf with us when we ride out beyond the Wall.” So Ghost joins them on their mission to investigate what the hell is happening with the wildlings, wights, and White Walkers.