A second prequel , titled " Vastra Investigates " , was released online on 17 December 2012 . At the end of a case , Vastra and Jenny converse with an officer from Scotland Yard and apologise for Strax 's violent wishes for the culprit 's punishment . Vastra explains Strax 's alien origin as well as her own to the officer , much to his astonishment . Vastra reveals that she was awoken by an extension to the London Underground and initially disliked humans , though that changed when she fell in love with Jenny . On the carriage ride home , Jenny notices it is beginning to snow and Vastra notes that the snow should be impossible because there are no clouds in the sky .