A third prequel , titled " The Battle of Demon 's Run — Two Days Later " was released on the United States iTunes and Amazon Video stores on 25 March 2013 . Two days after the events of " A Good Man Goes to War " , Vastra and Jenny convince Strax that he is not mortally wounded and invite him to accompany them back to 1800s London . The scene had been filmed as an extra due to the anticipation that fans would ask how Strax was resurrected and came to be in Vastra 's employ .