All That Remains started up sometime after the events of Season 1 and quickly led to Clementine and Christa alone in the woods. Where All That Remains really got going was after an attack that separated the two girls and left Clem alone. She eventually found a group living in a house, but suspicions were high on both sides. For some reason, the new group felt like she might belong to some other group run by a man named Carver. Meanwhile, after seeing what's happened to Clementine since the game started - it's no wonder she is a little wary of new people.
By the end of All That Remains, you not only convince the new group that you are good to have around, but you have to make a deadly split-decision choice between two of their members. Saving one most definitely leaves the other dead. Among other things, A House Divided will force you to deal with that choice.