Cardiff Rift

From "Boom Town" — The extrapolator and the TARDIS begin to rip open the Rift

The Rift first appears in the Doctor Who episode "The Unquiet Dead". This episode takes place in 1869, when the Gelth, gaseous humanoid organisms, pass through the Rift into a funeral parlour, where they are able to “possess” the corpses. It is established that the Rift releases radiation, prolonged exposure to which can grant psychic powers to people, including Gwyneth, a servant in the parlour. The Doctor speaks with the Gelth via Gwyneth in a séance, where they claim to be few in number following the Time War, and ask for the Rift to be widened, allowing the remaining Gelth to live in the corpses. However, after the Doctor discovers that the Gelth are in fact far more populous than first claimed, and intend to slaughter the human race to provide themselves with inhabitable corpses, Gwyneth sacrifices herself by causing a gas explosion, which seals the Rift and apparently kills the Gelth.

The episode "Boom Town", set in modern-day Cardiff, revisits the Rift. The Rift now runs through Roald Dahl Plass, and emits radiation which the TARDIS can harness for use as fuel. However, a member of the Slitheen crime family, Blon Fel-Fotch Pasameer-Day Slitheen, disguised as a woman named Margaret Blaine, becomes the elected Mayor of Cardiff and plans to build a defective nuclear power station on the Rift, which would then cause a nuclear meltdown. The resulting energy shockwave would destroy the planet, but allow Blaine to escape on a tribophysical waveform macro-kinetic extrapolator, described as a "pandimensional surfboard". The Doctor, Rose, Mickey Smith and Jack Harkness manage to foil her plan, but the extrapolator latches onto the TARDIS and causes the Rift to split open, which causes earth tremors across Roald Dahl Plass. The Rift is finally sealed by the TARDIS.

The Tenth Doctor and Martha Jones briefly revisit the Rift in "Utopia" to refuel, treating it as a "pitstop". The Doctor revisits Cardiff to drop off Jack Harkness in "Last of the Time Lords". In "The Stolen Earth", the Torchwood Three team and supercomputer "Mr Smith" use the energy of the Rift to send a signal to the Doctor through the Medusa Cascade. Later, in "Journey's End" the Doctor uses the Rift - after Mr Smith has interfaced with the TARDIS to allow it to lock on properly - as a towrope to literally ”tow” the Earth back to its proper location in time after it was stolen by the Daleks.

From "Kiss Kiss, Bang Bang" — the Rift before Captain John emerges.

The Rift features regularly in Torchwood, with almost every episode involving material or life-forms which have passed through the Rift. The Torchwood Institute website suggests that Torchwood Three was formed in Cardiff as soon as the Torchwood Institute became aware of the Rift's presence.[1][3] Torchwood Three has also been described as merely a "monitoring station" for the rift.[4] The website lists among the items found in the Rift "3 new Weevil clusters... [7] items of unknown provenance... 2 weapons... 2 EBEs".[3] However, the Rift appears to be one-way; craft sent through the Rift have been unable to either return or to send back a signal.[1]

In "Out of Time", the Rift facilitates the misplacement of people on board a plane from 1953 to the show's present day. In the episode's conclusion, a temporal immigrant, feeling it will take her home or somewhere new, ventures back into the sky, with her ultimate fate left unclear.

In "Captain Jack Harkness", the Rift is responsible for sending Jack and Tosh back to 1941. In the present day, Owen uses a "Rift machine" designed by Toshiko to open the rift and bring them back (this episode shows the Rift's event horizon properly for this first time).

The consequences of Owen's actions resonate in the next episode, the first series finale "End of Days". By opening the Rift, he has allowed more "flotsam and jetsam" to come through, including a Roman soldier, a group of mediaeval plague sufferers, and even a large UFO. As Jack puts it, opening the Rift has caused the cracks in time to widen on a global scale. The time travelling Bilis Manger shows Gwen a vision of the death of her boyfriend Rhys, convincing her to open the Rift even wider to reverse the damage that has already been done. When this happens, the entity known as Abaddon rises from "beneath the Rift". Jack sacrifices himself to destroy Abaddon, and the Rift immediately closes. The team (including Jack, who has come back from the dead again thanks to his past experiences) still retains the memory of what happened, but some of the actual events have been reverted (such as Rhys returning to life), and Owen spearheads a minor clean-up mission.[5] A year later in "Exit Wounds", Jack's brother Gray has Captain John Hart widen the rift again to unleash chaos across Cardiff, unleashing monsters such as Hoix, Weevils and cowled ghouls from distant times and places. As a Time Agent, Captain John can use his wrist-strap vortex manipulator to travel to Cardiff through the Rift.

In "Adrift", it is revealed that as well as depositing creatures and items in Cardiff, the Rift also takes people, depositing them anywhere in space or time. Gwen discovers that this is the cause of a drastic increase in the amount of missing people in the Cardiff area. The Rift, in an effort to right itself, often returns people again. However, they have often seen such graphic images that they develop mental illnesses.

At the start of Torchwood: Children of Earth (2009), the Hub is destroyed and Torchwood relocate to London as fugitives. Torchwood itself is later destroyed by the end of the serial. Fans were left asking the fate of, among other things, the Rift. The subsequent 2011 series of Torchwood relocates primarily to the United States. When asked in an interview with SFX magazine, Davies stated "I like to think that when [subsequent Doctor Who executive producer] Steven Moffat so thoughtfully closed all those cracks in the universe, the Rift in Cardiff closed up at the same time. I used to wonder what the hell happened to that Rift and now it's all solved. When I watched those cracks seal up I was like, 'Oh, thank you.'" This refers to the events of the 2010 Doctor Who episode "The Big Bang", which was written by Steven Moffat. However, Torchwood media in 2011 since provided a direct explanation for the Rift. In the radio drama "The House of the Dead", Jack visits a haunted location where the Rift allows ghosts, including the deceased Ianto Jones, to enter into the living world. To close the Rift forever and seal an ancient evil on the other side of it, Jack creates a device designed to seal the Rift. The device will also provide Jack an end to his cycle of resurrections. However, Ianto's spirit tricks Jack into leaving, and detonates the device himself, closing the Rift "forever" and with it the barrier between the living and the dead.[6]

In the Torchwood novel Border Princes by Dan Abnett, it is revealed that several other planets border permanent points where the Rift has anchored. One such planet has a similar organization to Torchwood entitled The First Senior, whose title for the Rift translates as The Stumble, The Misstep or The Border. When The First Senior heard of Torchwood, they inserted a Principal, a spy who could observe how they handle the Rift, purely for research into how other "Rift guardians" operate. Like all Doctor Who and Torchwood spin-off media, its place in canon is unclear.