. . . . "The Poison Sky"@en . "4"^^ . "5"^^ . "The Poison Sky"@en . . . . "2008-05-03"^^ . "Douglas Mackinnon"@en . . "220"^^ . . "The Poison Sky is the fifth episode of Series 4 and the second of a two-parter starting with The Sontaran Stratagem."@en . . . "When will they learn?"@en . . . . . . "The Poison Sky is the fifth episode of Series 4 and the second of a two-parter starting with The Sontaran Stratagem."@en . . .