 According to the character's creator and executive producer Russell T Davies in his non-fiction book "", the character was developed from the beginning with the intention of appearing for a whole of the 2007 series, and to later make guest appearances in subsequent series and crossover appearances in the show's two spin-offs; Martha subsequently made guest appearances in "Torchwood" series two and in "Doctor Who" series four in 2008 and special episode "The End of Time" in 2010.Martha was also intended to make guest appearances in the 2009 series of "Torchwood" and "The Sarah Jane Adventures", but could not due to the actress's other work commitments.Within the series' narrative, Martha begins as a medical student who becomes The Doctor's time travelling companion after an incident at the hospital where she works.