 As a black time traveller, the character of Martha allows "Doctor Who" to explore historical issues concerning race.In the episode "The Shakespeare Code", Martha wonders if she is safe in an era before emancipation, but the Doctor is unconcerned.The Doctor points out to Martha (also the audience surrogate) that England in 1599 is "not so different from your time"; black women are seen walking amongst the crowd at home and safe, and Martha identifies several cross-dressing actors.