Holding cells (Torchwood Hub)

The holding cells referred to a room of prison cells within the lower corridors of the Torchwood Hub. (TV: Exit Wounds) They were used to both contain and quarantine dangerous creatures and individuals. The cells could be opened and closed through use of a swipe card. (TV: Day One) While they were mostly used for short-term containment, there was one long-term resident: a Weevil which Jack Harkness named Janet. (TV: Day One, TV: Combat) Janet had been captured shortly before Gwen Cooper joined Torchwood Three. (TV: Everything Changes)

The cells were dungeon-like. Three of the four walls of each cell was made of rough, dank stone. The fourth wall was a thick transparent plastic with neat air holes drilled into it. Beyond the plastic was corridor with another stone wall beyond that. The entire area was soaked in a dim reddish light. (PROSE: Bay of the Dead)

History
Torchwood Cardiff operated cells as early as 1899, when Jack joined the Torchwood Institute. A Blowfish was briefly taken to a cell before being shot dead by Alice Guppy, who prefered to kill aliens rather than keep them in long term storage. (TV: Fragments)

Carys Fletcher was briefly kept in a cell while she was possessed by the Sex Gas. She was able to escape by exerting her influence over Owen Harper, allowing her to take his swipe card. (TV: Day One)

Jack noted that, as they were mostly made of liquid, a captive Arcan would make a mess of the cells. It was partly for this reason that he felt it better to simply warn off the crew of an Arcan leisure crawler rather than attempt to apprehend them. (TV: Cyberwoman)

Ianto Jones pleaded with Jack to let his girlfriend, Lisa Hallett, stay in the cells; Lisa, having been partially converted into a Cyberman, had attacked the team. Jack refused and ultimately led the team in killing her. (TV: Cyberwoman)

Max Tresilian, a pawn of Suzie Costello, was taken to the cells by Torchwood. (TV: They Keep Killing Suzie)

When Torchwood was trying to find the Weevil Fight Club, they let Janet loose and used her telepathic senses to find other Weevils. Janet almost killed Owen before being recaptured. Following his ordeal, Owen stood outside the cells, where he successfully intimidated Janet and another captive Weevil. (TV: Combat)

After the Cardiff Space-Time Rift fractured, a temporally displaced Roman soldier was captured and taken to the cells along with multiple Weevils. By this point, the Hub was full in all vaults across all nine levels. Jack gave Ianto his approval to activate the vaults below, which Ianto noted had never been used since he joined Torchwood Cardiff. Outside the cells, Ianto encountered an apparition of his dead girlfriend, Lisa Hallett, who told him to open the rift.

Later, Gwen forcibly took her boyfriend, Rhys Williams into the cells for his own protection. However, Rhys' cell door spontaneously opened. Stepping out of his cell, Rhys met Bilis Manger, who stabbed him to death. Rhys' body was soon found by Jack and Gwen. When the Torchwood team opened the rift despite Jack's warning, both the Roman soldier and Rhys' corpse vanished while the Weevils went into a frenzy as Abaddon arrived. After Abaddon was killed, Rhys reappeared at his home, with no memory of being detained or killed. (TV: End of Days)

Beth Halloran, a sleeper agent of Cell 114 was briefly brought to the cells by Torchwood. Whilst there, Janet visibly cowered in her presence. (TV: Sleeper)

During Adam Smith's time with Torchwood, Jack briefly saw an apparition of his younger brother, Gray, in the cells. Eventually, Jack imprisoned Adam after realising that he was a memory-changing entity who had infiltrated the team. Ultimately, all the members of the Torchwood team took retcon to forget Adam, resulting in him disappearing from existence. (TV: Adam)

Billy Davies, an agent of the Pharm, was captured by Torchwood and taken to the cells. In order to interrogate him, Ianto Jones brought in Janet, whose chain brought her mere inches away from him. Ianto got rid of her by using anti-Weevil spray. The team intended for Billy to take them back to the Pharm when the mayfly within him began to hatc. Owen Harper tried to use the singularity scalpel to save him, but exploded his stomach. (TV: Reset)

Following his death and subsequent resurrection, Owen found that all Weevils feared him. Outside Janet's cell, Owen observed that he was "King of the Weevils". (TV: Dead Man Walking)

Jack warned Owen that he would be confined to the cells if he refused to comply with Martha Jones' tests and examinations. (TV: A Day in the Death)

Gray used his wrist strap to release Janet and the other Weevils from their cells. Running amok in the Hub, the Weevils briefly menaced Gwen, Ianto and John Hart before being shot down and returned to the cells. The three were themselves locked in the cells by Gray, however, they were later set free by Jack. (TV: Exit Wounds)

Ianto locked a zombie, which Jack named Mildred, in the cell next to Janet's during an outbreak in Cardiff. (PROSE: Bay of the Dead)