The Exodus Theory aka The Exodus Hypothesis aka The Exodus Strategy aka The Exodus Strategem (sic) aka The Exodus Stratagem (sic)
"The Sontaran Stratagem"
Doctor Who episode
"The Sontaran Stratagem" is the fourth episode of the fourth series of British science fiction television series Doctor Who. It was broadcast on BBC One on 26 April 2008. The episode features the return of former companion Martha Jones, as well as the return of the alien Sontarans to the series. It is the first of a two part story, followed by "The Poison Sky". This is the Sontarans' first appearance since the 1985 Colin Baker story The Two Doctors.