We watch "The Sontaran Strategem" (Series 4, Episode 4) where the Doctor and Donna travel to Earth to return the 'forgotten' phone of former companion Martha. Whilst there, the Doctor reunites with alien Potato-Heads, Martha doubles her pleasure and Donna doubles her fun watching her grandfather slowly asphyxiate. All this and deadly self-driving cars? Thank god this is just science fiction. Wait...what?