Did anything important happen last week on Game of Thrones? I couldn’t remember, so thankfully, “Breaker of Chains” picks up where “The Lion and the Rose” left off — with a bereaved Cersei holding a dead Joffrey and screaming for Tyrion’s head, convinced that he’s responsible for the wee king’s death. The audience learns who’s responsible for the king’s death — both immediately, as Ser Dontos is implicated, and more remotely, when Sansa Stark arrives on the boat and Littlefinger makes his first appearance of the season.