Series 4 ( Torchwood ) Series 4 of " Torchwood " consisted of ten episodes broadcast between 8 July 2011 and 9 September 2011 . Like series 3 , the season carried an umbrella title — in this case , " Miracle Day " . This season marked a major departure from past " Doctor Who " - franchise productions , as it was a co - production of BBC Wales and the American cable network Starz , and was filmed in both Wales and Hollywood . The episodes of " Miracle Day " were broadcast on Starz in the US several days before their broadcast on BBC One in the UK . Production occurred after an aborted attempt to interest the Fox network ( which had aired the 1996 " Doctor Who " tele - movie ) in mounting a fully Americanised remake . The Starz / BBC production is a continuation of existing canon , set two years after the events of TV : " " and featuring several returning cast members , primarily John Barrowman , Eve Myles and Kai Owen , along with several scripted references to the Doctor and creatures from both " Doctor Who " and " The Sarah Jane Adventures " . A trailer for the series was released . Overview . When C . I . A . agent Rex Matheson investigates a global conspiracy , he finds himself unearthing a threat which challenges the entire human race . One day , nobody dies . All across the world , nobody dies . And then the next day , and the next , and the next . People keep ageing . They get hurt and sick , but they never die . The populace of the planet dub this " Miracle Day " for the immortality they now seem to have . However , this leads to a negative result : a population boom , overnight . With all the extra people unable to die and continuing births , resources have become limited . It ' s suggested that in four months ' time , the human race will cease to be viable . But this can ' t be a natural event – someone must have caused " Miracle Day " . It ' s a race against time as C . I . A . agent Rex Matheson investigates a global conspiracy . The answers lie within an old , secret British institute . As Rex keeps asking “ What is Torchwood ? " , he ' s drawn into a world of adventure , and a threat to change what it means to be human , forever . The answers seem to lie within Torchwood itself . But Torchwood ( 3rd branch ) was destroyed , years ago , and the keys to the institute are held by its only two surviving agents : former Police Officer Gwen Cooper , who has long since disappeared along with her husband and child , and the mysterious Captain Jack Harkness , a man whose history seems to stretch back for centuries and has disappeared off the face of the earth . Things become even more complicated as Rex soon becomes one of the people continuing to live thanks to " Miracle Day " . Luckily , Gwen comes out of hiding and Jack returns to Earth to help . Combining their experience with bizarre situations and information gathered from one of Rex ' s contacts , a new Torchwood team takes shape . Adding to the bizarre circumstances , Jack has lost his immortality . While some pharmaceutical companies take advantage of the people needing pain killers , Jack begins to think that something from his past may be causing " Miracle Day " . " Miracle Day " was written by Russell T Davies and co - produced by BBC Wales , BBC Worldwide and Starz Entertainment . It starred John Barrowman as Jack Harkness , Eve Myles as Gwen Cooper , Mekhi Phifer as Rex Matheson , Alexa Havins as Esther Drummond , Bill Pullman as Oswald Danes and Arlene Tur as Dr . Vera Juarez . It also featured the television debut of Anwen Williams , Gwen and Rhys ' s baby daughter , who was born during the interim between series 3 and 4 of " Torchwood " . It was primarily set in Wales and the US . The series covers an arc in which death ceases to exist on Earth . Digital availability . Series 4 of " Torchwood " is available for purchase and / or as part of a subscription on :