Blue Boxes (audio story)

Blue Boxes was the eleventh story of the tenth season of Big Finish Productions' Short Trips series. It featured the Third Doctor and Liz Shaw.

Publisher's summary
Death stalks the phone lines.

UNIT's been inundated with prank calls. Bored, the Doctor agrees to help Liz investigate. Quickly immersed in the world of phone line hackers, it is revealed that they're being killed, one-by-one. With the death toll rising, the Doctor will have to use all his cunning and wits to defeat a foe he can't even talk to.

He'll also have to use a blue box. Just not the one you're expecting.

Plot
Kenneth Whitby, also known as the Twilight Trickster, is cracking the telephone lines at a phonebox in Chichester when he hears a sound and drops dead with a look of fear on his face.

Liz has managed to get the Doctor to help investigate a series of prank calls to UNIT from public phoneboxes and they contact Emily Chung at the University of Cambridge to learn about phreaks. They put together a blue box and find the phreaks' party line and learn from them about Whitby's death, after which they check his autopsy.

At Waterloo station, Siobhan Reilly answers a payphone and hears a buzz. She feels sick and the line goes dead.

Liz looks into mysterious occurrences involving phones and hears about Siobhan, whom she visits in hospital. Siobhan produces a cry like a sound Liz had heard on the party line and she tells the Doctor. The Doctor modifies the blue box and connects it to the TARDIS; the TARDIS makes the noise, leaving Liz unconscious and Emily in need of a visit to the sick bay.

The Doctor believes that they are dealing with an Antiphon, something commonly used on spacecraft. In this instance, it seems to be a distress call which has targeted UNIT HQ after detecting the TARDIS and is likely located near the construction of the new wing at the National Gallery. They find that the Antiphon belongs to a probe sent out by aliens wiped out by a virus and the Doctor shuts it down.

Characters

 * Third Doctor
 * Liz Shaw
 * John Benton
 * Emily Chung
 * Siobhan Reilly
 * Kenneth Whitby

Worldbuilding

 * The Doctor reminds Liz of Sherlock Holmes.
 * Liz had never been close to her doctoral supervisor at the University of Cambridge.
 * Phone crackers are known as phreaks.
 * Chung mentions phreaks Joybubbles, who is blind, and Crunch.
 * In some centuries on Draconia, slight tonal imbalance can mean a grave insult to a Draconians' brood circle.

Continuity

 * The Doctor mentions the Mars Probe 7 affair. (TV: The Ambassadors of Death)
 * The Doctor mentions Block Transfer Computation (TV: Logopolis, etc.) and Draconia. (TV: Frontier in Space)
 * The Antiphon is activated by the building of a new wing at the National Gallery. (TV: The Day of the Doctor)
 * The Doctor comments "My aunt Flavia, who actually is hundreds of years old." (TV: The Five Doctors)