Day One (Torchwood)

02 – "Day One"
Torchwood episode
The Gas takes over Carys's body.
Cast
Starring John Barrowman – Captain Jack Harkness Eve Myles – Gwen Cooper Burn Gorman – Owen Harper Naoko Mori – Toshiko Sato Gareth David-Lloyd – Ianto Jones
Others Kai Owen – Rhys Williams Adrian Christopher – Private Moriarty Ross O'Hennessy – Sgt. Johnson Sara Lloyd Gregory – Carys Ceri Mears – Banksy Justin McDonald – Matt Tom Price – PC Andy Davidson Brendan Charleson – Ivan Fletcher Rob Storr – Gavin Alex Parry – Eddie Gwynne Felicity Rhys – Bethan Naomi Martell – Receptionist Donald Longden – Mr. Weston
Production
Directed by	Brian Kelly
Written by	Chris Chibnall
Script editor	Brian Minchin
Produced by	Richard Stokes Chris Chibnall (co-producer)
Executive producer(s)	Russell T Davies Julie Gardner
Music by	Murray Gold Ben Foster
Production code	1.2
Series	Series 1
Running time	48 mins
First broadcast	22 October 2006 (2006-10-22)
Chronology
← Preceded by "Everything Changes" Followed by → "Ghost Machine"
List of episodes

"Day One" is the second episode of the first series of the British science fiction television series Torchwood. Directed by Brian Kelly, the episode was first broadcast on the digital channel BBC Three on 22 October 2006 with the series pilot, "Everything Changes", and later repeated on terrestrial channel BBC Two on 25 October. It was the first work in the Doctor Who universe to be written by future Doctor Who showrunner Chris Chibnall.

The episode centres on Gwen Cooper (Eve Myles) working her first case with the alien hunters Torchwood in Cardiff, when she lets loose a purple alien gas^{[broken anchor]} that survives on the energy of orgasms. Over the course of the episode, the team hunt for Carys before the gas kills her.

Originally entitled "New Girl", the episode was written to interpret Gwen's "first day in hell". On the sex gas, series creator Russell T Davies stated "when we're launching a new adult science fiction drama, it's kind of inevitable you're going to do the sex monster". The episode was filmed during a three- to four-week period in May 2006, with much of it filmed before the first episode in the same production block. "Day One" was originally seen by 2.3 million viewers, making it one of the highest-rated BBC Three broadcasts of all time, but was met with generally mixed reviews.