 It first aired on October 8 , 2009 in the United States , and was watched by more than 6 @.@ 02 million viewers . The episode received generally positive reviews , with many critics praising the new revelations about the shapeshifters , the parallel universe , as well as the much @-@ anticipated conversation between Olivia and William Bell . In January 2013 , IGN ranked it as the third best episode of the series . 
