Cell 114

Cell 114 was the official designation for a group of sleeper agents of a species that Jack Harkness was aware. Very little was known about them, since they didn't usually leave survivors, though he did know that he carried out stealth alien invasions.



History
The Cell was in the process of infiltrating the Cardiff area on Earth until Torchwood 3 became aware of them in 2008 after inexplicably fierce attacks on two burglars who had invaded the home of one of the agents, Beth Halloran, who thought of herself as an ordinary Human. When Torchwood discovered the Cell 114 presence, other agents they activated, and tried to set in motion a plan to explode nuclear missiles stored in an old mine near the city. This attempt was thwarted by Torchwood. However, one of the agents told the team that there were more members of the invasion fleet already on Earth.

Methods and technology
They tended to infiltrate planets, first with an advanced guard, sometimes watching for years, until they knew all they wanted to know about the species and were ready to take over. Apparently, agents were modified to resemble the native species, though with implants which could take the information and transmit it to the main invasion fleet. These implants even had built-in weaponry such as spikes and explosives. As well as visually resembling the natives, Cell agents could generate false sensor images as well as a personal force field less than a nanometer around their body (mainly the arm where the implant was stored) for protection.

Their main resource seemed to be the aforementioned implant located in the left arm (at least when mimicking Humans), which contained collected data and transmitted it to the main invasion fleet. They also contained at least one small bomb for sabotage or self-destruction. Furthermore the arm could be transformed into a sharp spike for close combat. In the case of Beth Halloran, a threat to her life, in the form of a burglar, caused her alien personality to awaken, take over and swiftly kill the intruders. (TW: Sleeper)