"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 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.
Plot
Gwen is called into work at Torchwood early when a meteor falls outside of Cardiff, cutting her date with Rhys short. As the Army secures the area, Torchwood investigate the meteor. Gwen's colleague Owen taunts her by calling her the "new girl". In an attempt to retaliate, she throws a chisel at him, but misses and cracks open the meteor, allowing a purple gaseous entity to escape. The gas finds a young woman, Carys Fletcher, outside a nightclub and takes her host. In the club, a possessed Carys seduces a man and takes him to a restroom, where they proceed to have sex. At the moment of climax however, the man dissolves into dust while Carys absorbs the energy that remains.
Torchwood become aware of the bizarre death and realises through CCTV that the gas has taken over Carys. They later find where Carys lives and arrive there before she could harm a postman. When she tries to escape, Owen traps her using a portable prison cell. Carys is placed in a holding cell in Torchwood's hub. As tests are run on Carys, Gwen feels uncontrollable urges to kiss her, showing that Carys is emitting high levels of pheromones, effectively becoming a "walking aphrodisiac", but the gas is also slowly killing her. Later, Carys escapes from her cell after seducing Owen.
In an attempt to capture her again, Torchwood run on Toshiko's hunch that she will be after her ex-boyfriend Eddie; they arrive at his house to find Carys already killed him. Later they discover Carys works as a temp at a fertility clinic. They race to the clinic to find Carys has been inside for some time killing some of the clients. After eventually cornering Carys, they find that she has moments before she dies. Jack buys her some time by kissing her, transferring some of his "excess" of life onto her. Gwen offers the gas presence her own body as a host to save Carys. When the gas leaves Carys, Jack throws the portable prison cell at it. Since it cannot survive in Earth's atmosphere for long, the gas dies out. As Gwen leaves for home, Jack advises Gwen not to let the job consume her because her perspective is important to the team. He then encourages Gwen to go home and spend time with Rhys.
Production
Writing
The working title for the episode was "New Girl", which changed to the current "Day One" by the beginning of October 2006. Head writer Chris Chibnall, who wrote the episode, found that writing the second episode was hard, as there was a challenge to demonstrate how Torchwood works, and set the formula for the rest of the series. He wanted to write an episode that would centre on Gwen about her "first day in hell", and show the audience that Torchwood is unlike any normal job, as one small mistake can have major ramifications on the city. The scene where Gwen accidentally opens the meteor was meant to "extend the metaphor of breaking the photocopier on your first day at work". It is also set to show the separate dynamic between the team and Gwen. Series creator Russell T Davies stated that as the rest of the team are for the aliens, science, technology and mythology, Gwen is for "the people"; she's the only person in the team who cares about what happens to Carys. Eve Myles also noted in the episode's audio commentary that throughout the episode, it added a mix between her domestic life and the science fiction.