The Wire

"Now, are you sitting comfortably? Good, then we'll begin."

- The Wire.

The Wire is an alien life form that was branded a mastermind of the planetHermethica's crime sydicates and  executed by its people. It managed to preserve itself as a being of plasmic energy, because it guard's communication device was on as he was illegally recording the execution. It escaped to Earth in this form.

It concealed itself in television signals, transferring itself from set to set. It fed off the mental signals of Humans, paralysing them and then leeching out their energy with electrical tendrils (DW: The Idiot's Lantern) This process would leave the victim mindless, as well as faceless. Rose Tyler suffered this fate when she started investigating the phenomenon. The victim's consciousness was retained in tact, as seen when the Wire showed the Doctor a sampling of its victims on the televisions in Magpie's shop. The Wire used the image of a female BBC continuity announcer to communicate with the outside world. It hoped to use this energy to manifest itself in a corporeal form once more.

The Wire stole the face of Mr Magpie, who owned an electrical shop, and gave it back to him, giving him plans for then-future technologies (such as televisions small enough to carry in one hand) and promising freedom to him after the completion of its simple two-phase plan: First, have Magpie sell cheap television sets all over North London so it could feed. Second, have Magpie connect the Wire (inside a portable television) to the television transmission tower at Alexandra Palace on Queen Elizabeth II's coronation day, June 2, 1953. Connected to the tower, the Wire could both transmit itself to the estimated three million viewers watching in the vicinity and transmit back energy it could use to re-constitute its body.

However, the Doctor was able to trap the Wire on a Betamax tape using a makeshift video recorder. The Wire's victims were then restored to normality. The Doctor seemed confident that the Wire would remain trapped, but said that he would tape over it, just to be safe. (DW: The Idiot's Lantern)

The Wire resurfaced some 30 years later, in another attempted invasion though television. This was known as the "Bee-Tee Incident", but it has never been officially confirmed or denied.
 * All additional information is recorded on page 92 of the book Creatures and Demons.