The Blue Tooth was the third story in the first series of The Companion Chronicles. It was produced by Big Finish Productions. It was written by Nigel Fairs and featured Liz Shaw. It was notable for being the one of the few stories to pit the Third Doctor against the Cybermen. Until the publication of The Piper in 2015, this was the only Third Doctor story to use the Cybermen as its main antagonists.
"I suppose that was one of the Doctor's most endearing qualities: the ability to make the bizarre and the terrifying seem utterly normal."
When Liz Shaw's friend Jean goes missing, the Doctor and U.N.I.T. are drawn to the scene to investigate. Soon Liz discovers a potential alien invasion that will have far-reaching affects on her life... and the Doctor is unexpectedly re-united with an old enemy...
Liz Shaw recalls her first meeting with Jean Baisemore and her time with UNIT and why she left. She recalls a time when she was working for UNIT and during a day off she went to the visit Jean and they were to meet and have lunch at the Copper Kettle. However, when she didn't turn up, Liz went to investigate, starting with Jean's cottage in Oakridge. She finds the interior a mess and Jean's dead cat and attempts to contact the Doctor, who alerts her that he was already on his way with the Brigadier, informing her that it's not the first as a string of deaths related to Cambridge scientists has appeared within the last week. The Doctor arrives and they investigate. Eventually he discovers teethmarks...
The Doctor and Liz search for the source of where the teeth-marks may have come from and eventually find a small tunnel dug in the garden. They join the Brigadier in a similar crime scene but for property not belonging to a scientist which throws a wrench in the Doctor's theory, until he shows them that all the victims had the same dentist, the university dentist. Liz reminisces during the car trip to HQ about more times with Jean at Cambridge until she is awoken by the Doctor who informs her there'll be split up and she'll be going with Captain Yates to investigate the dentist. Liz books an appointment for ten minutes time but when she sits down in the waiting room she is knocked out. Struggling, she barely escapes with the Doctor's help when he finds her. After she makes a recovery the Doctor explains to her what happened. First, they find Andrew Cull, the cleaner whose house they had investigated, had tried to commit suicide, however, the Doctor, having examined his remains, discovered that the train sliced him in half but his body remained intact, something that isn't possible for a human body. Secondly, Andrew's body had been made of metal. In the moratorium, the Doctor and Liz examine the body better, and discover a blue metal, after which the Doctor confirms Liz's hysterical guess that somehow the metal was transferred into his body. Mike finds Liz's purse after he went back to investigate again, but her UNIT ID pass is missing. Liz examines the body further but it begins to spasm and cybermats begin to emerge from the body's shoulder. Sergeant Benton and Broadwick come in to help Liz when they hear her scream, however, they end up trapped by the creatures...
Benton distracts the cybermats while Liz sprays them with a fire extinguisher which momentarily stops them. The Doctor examines and identifies them back at UNIT HQ, explaining that they are up against the Cybermen. The Doctor explains that the blue metal used by the dentist for fillings, once activated, consumes the patient and uses their body to produce Cybermats. He then examines Liz's new filling from the dentist, only to discover it is blue, confirming his suspicions. He informs Liz that he has already developed a way to stop the blue metal's growth in a similar way that the chemicals in the fire extinguisher were able to stop the Cybermats. He assures Liz not to worry and that she will be fine for the time being. However, Liz begins to black-out and explains the strange things she did while presumably under the influence of the blue metal. Eventually she and the Doctor end up at the edge of the airfield, where she tries to get away from the sunlight and digs a hole in the ground which she enters, after which the Doctor follows. It turns out to be the interior of a crashed Cyber-ship which seemed to draw her in like a homing beacon. Liz, unwillingly, knocks out the Doctor and blacks out again herself. Upon awakening, she finds herself strapped down with tubes inserted into her and she sees her friend Jean, who is in the process of being cyber-converted and in her last moments of life, tells Liz she was late because she forgot her keys, then begs Liz to kill her. However, before Liz can respond, the Cybermats kill Jean. The Doctor, also strapped down, tells her to resist as a Cyberman approaches them. The Doctor and the Cyberman discuss its plan for invasion but it is a swift chat as the Doctor fails to convince the Cyberman of its own individuality. It prepares to convert them both...
The Doctor uses his sonic screwdriver to get out of the casket and rescues Liz from hers. Liz looks around and is horrified by the conversion caskets she sees with the figures inside being taken over slowly by the blue metal but the Doctor tells her to keep moving. They find the dead Cyberman pilot of the ship however the Doctor realises what has really happened, just as they are found by the same Cyberman as before. The Doctor manages to get the Cyberman to reveal that it was not originally one but was a human named Gareth Arnolds who discovered the crashed ship that had no survivors, but as a scientist was intrigued by the technology inside that he did not understand. He experimented with the blue metal, first on the pilot (which was missing its legs), then on other humans and is now building a Cyber-army out of it and them to convert the rest of the planet. Liz and the Doctor attempt to escape as they are followed by the Cybermen but they eventually get cornered. However, the Doctor tries to stir the last of Gareth's mind unsuccessfully, when suddenly Liz feels enormous pain in her mouth and blacks out.
She awakens on Jean's sofa and the Doctor explains what happened. The Doctor only had enough newly developed antidote for Liz and so had to put an end to Arnold, lamenting that he wasn't able to do more and that once he was eliminated the rest of the Cybermen created from the blue metal simply went back into stasis with no one to receive orders from. He also reveals that Jean was confirmed dead, to a shocked Liz. However, he expresses confidence in Arnold's work, saying that he hopes to explain to the Brigadier how they should do some more scientific investigation into the blue metal and Arnold's work. When Liz asks what was in her mouth the Doctor shows her the dead Cybermat and her broken tooth, much to her disgust. It is also revealed that Arnolds was, in fact, the dentist at the university. As Liz lets this information sink in, the Doctor sees the Brigadier out front, and when he looks inside Mike's gun to find his original compound for destroying the cybermats being used and not the antidote, he is disgusted with the Brigadier, who ignores him and orders the men to finish killing the rest of the Cybermen in the crashed ship. The Doctor sadly walks out, leaving a thoroughly upset and depressed Liz inside the cottage.
- The electricity board threatens to cut off the power at UNIT HQ because the Doctor is using large amounts of power for his experiment on the TARDIS.
- Liz was at the University of Cambridge in the 1960s alongside Jean Baisemore.
- Liz doesn't like dentists.
- Liz almost doesn't recognise the decimal coins in her purse while under the influence of the anesthetic.
- Liz's UNIT ID gets stolen.
- While under the influence of the blue metal, Liz almost eats a copy of the Encyclopaedia Britannica.
- Liz had a choice between Newnham College and Girton College while at Cambridge. She chose Newnham.
- The phosphorus tribromide as part of a larger compound is able to slow the growth of the blue metal to virtually zero.
- This story was recorded at The Moat Studios.
- While originally set for release in January 2006, it was announced on 1 February that the release of the first series of Companion Chronicles was to be delayed until 5 February. The announcement of their release came on 19 February, however this followed a gap of communications since the original announcement that release was delayed, so it is difficult to pinpoint a more precise release date than February.
- This marks the first appearances of Liz Shaw, Sergeant Benton and Captain Mike Yates in an audio drama.
- To date, this is the only appearance of the Cybermen in the Companion Chronicles.
- Aside from a brief appearance in AUDIO: Zagreus, this is the first Big Finish audio drama to feature the Third Doctor.
- Liz refers to Mike Yates as "Captain Yates", which is at odds with his rank as given in PROSE: The Scales of Injustice but consistent with AUDIO: Vengeance of the Stones.
- This story takes place after TV: Inferno.
- Unlike most Companion Chronicles, this episode is divided into four 15-20 minute parts as opposed to two 30 minute parts. As a result, it is slightly longer than most single-disc releases.
- This story was told from Liz's perspective.
- Liz says she lived with her mother whilst studying for her undergraduate degree. (AUDIO: The Last Post)
- Later in his timeline, the Third Doctor would briefly encounter the Cybermen on the Death Zone on Gallifrey, (TV: The Five Doctors) and a longer encounter on the human colony of Burnt Salt with Jo Grant. (AUDIO: The Tyrants of Logic)
- Liz emphasizes her disdain for UNIT throughout the story, and even mockingly mentions invisible ink, a line she smugly tells Brigadier Lethbridge Stewart during their first meeting. (TV: Spearhead from Space)
- The Doctor arrives in Bessie. (TV: Doctor Who and the Silurians et al.)
- The Brigadier remembers the Cybermen from their previous invasion. (TV: The Invasion)
- The human who turned himself into a Cyberman in this story is named "Gareth Arnolds". The tenth Doctor and Angela Price investigate a Cyberman who was originally a human named Sally Phelan, who was supposed to marry a man named "Gareth", who presumably was also converted into a Cyberman in the same episode. (TV: The Age of Steel)