Enemy Aliens (audio story)

Enemy Aliens was the eighth release of the Destiny of the Doctor audio series, produced by Big Finish Productions for AudioGO.

Publisher's summary
1935: a message from a Time Lord in trouble sends the Eighth Doctor and Charlotte "Charley" Pollard to the streets of London's West End, in search of a mysterious alien adversary — unaware that something monstrous is already on their trail.

They soon discover that an insidious conspiracy is indeed at work, its tentacles extending the length of the British Isles. Proving its existence won't be easy, however, after a confrontation in a music hall ends up with the Doctor under arrest and Charley on the run, suspected of murder. All their hopes rest in a musical clue and a man named Hilary — neither of which are much consolation, with the two time travellers the object of a nationwide manhunt.

And all the while, the enemy aliens are drawing closer and closer still...

Plot
The Eighth Doctor and Charley Pollard, fresh off a series of adventures, try to relax in the TARDIS—but the Doctor is interrupted by a message from himself. More to the point, it's a future incarnation, leaving a badly-recorded message on a tape deck in the console. Part of the message is missing, but it warns them about some enemy aliens—and... William Tell?

The TARDIS leads them to London in 1935—pointedly not the fourteenth century, the home of William Tell—where a strange electronic fuzz blankets the area and blinds the TARDIS sensors. Charley irritates him by humming the William Tell Overture repeatedly, leading the Doctor to think of Rossini, the author of the overture. As they depart, a group of local boys take up the overture, but are menaced by an unseen creature. The Doctor locates a music hall, where a man named William Tell is performing feats of memory. The Doctor puts him to the test, and catches him in some numerical inaccuracies; he then challenges him about "enemy aliens". Tell, acting strangely compelled, says that the "key is in the house of the straggly witch"—and then he is shot dead. Charley finds the murder weapon, but is immediately accused of the murder. The police arrive and take on the Doctor, while a man named Hillary Hammond rushes Charley out of the building.

Charley awakens to find herself in an unknown flat with Hammond, who is humming the overture. She insists on finding the Doctor, but Hammond refuses to let her leave; he says that she is in the newspaper regarding the murder. However, the article indicates the Doctor also escaped. They are interrupted by a window breaking downstairs. They flee the apartment, and head to Scotland by train; Hammond explains that "the straggly witch" is a colloquial name for a bay in Scotland, and believes the Doctor would have worked it out and gone there. Along the way, Charley dons a sailor uniform as a disguise; she also mentions having survived the crash of the R101, and mentions the TARDIS as well. Nevertheless, the police invade the train at a stop anyway, with a military escort. Charley tries to hide, and finds a coffin in the baggage compartment... with the Doctor inside! He admits to avoiding not only the police, but also the mysterious aliens, which he believes attempted to attack him at one point. The Doctor is forced to jump off the train and into a river, narrowly avoiding being shot by the soldiers. Charley is able to evade them and return to Hammond, but he is not alone. He is accompanied by two elderly women, who claim they want to help.

The four disembark at a small village, and Hammond says that the two old ladies believe that he and Charley are eloping. They are escorted to the church; Charley is outraged at the thought, but Hammond appears to be seriously suggesting it, on the basis that it would get them out of trouble with the police by changing their identities (as Hammond is using the name "John Smith"). Charley momentarily considers it, given that she herself is presumed dead after the R101 disaster, but she declines. Shortly thereafter, the Doctor arrives on horseback; Charley is amazed to see that he is alive. He is being pursued, however, and so they hide in the church. Charley takes advantage of the situation to suggest that they go through with the wedding, for the same logic that Hammond had used, but the Doctor realizes that the two old ladies were also in the audience at the music hall. The women produce pistols, and the Doctor and Charley are forced to run. They come upon a group of individuals, whom they recognize as Germans—a different kind of "enemy aliens".

The Germans leave them in a cell in a ruined castle overlooking the "straggly witch" bay. Hammond arrives and takes them out of the cell, and down to a hidden jetty in a cave—not a "secret key", but a "secret quay" leading to a hidden "loch", not "lock". Hammond reveals he is working for the Germans, and that he killed Tell because the Doctor got too close; Tell's incorrect statements were actually coded communications in use by the Germans. As Tell exposed the straggly witch location, where the Germans came ashore, they are obligated now to pull out of that location. He admits he would have killed Charley as well, had she married him, which would have allowed him a new identity as a widower. He has also brought the TARDIS here, based on the things Charley let slip. He also mentions a strange radio transmission that had led him to believe the TARDIS was real; he plays a tape of the message from the future Doctor, including the part. The future Doctor makes it clear that the electronic fuzz is preventing him from contacting his other incarnations; he wanted the Eighth Doctor to clear the interference. The aliens in question—actual aliens, not the Germans—are using the overture via radio broadcast to coordinate their plans, much as Tell was doing for the Germans. Hammond wants the Doctor to give him the secrets of the TARDIS; but they are interrupted by mortar fire. The Doctor reveals that the two old ladies were actually agents for the British, who have now initiated an attack on the German position. In the chaos, the Doctor and Charley escape in the TARDIS.

Thirteen hours later, the TARDIS materializes in London. Charley checks the Radio Times, and learns that a pianist will be broadcasting Rossini's overture shortly—the signal to begin the invasion. The Doctor says that they waited until the last minute so that the pianist could not be replaced in time; he is horrified to realize that the broadcast will be worldwide. Before they can move on the radio station, a large alien brute arrives from the direction of Hammond's vacated apartment—and purrs at Charley. She realizes it must have been the creature that broke into the downstairs flat; and it has been waiting for her. The Doctor realizes that it is an advance sentry—and Charley had activated it by humming the overture. Now it is at her command.

The Doctor, Charley, and the creature rush to the broadcast studio, and interrupt the broadcast just before the overture. However, it's too late—the alien mothership over London is appearing. However, the electronic fuzz is now gone; and the Doctor is free to send a radio signal. He sends a 20,000-terrahertz signal to the ship; the resulting wave disturbance is enough to give the aliens pause. They go to the roof to watch the ship respond. But, the Doctor realizes, his future self is also coming to their aid; the future Doctor sends a second signal, warning the aliens that Earth is protected by a race with higher technology than theirs. The ship—and all its companions around the world—depart.

Hammond meets them as they start to leave the roof, and threatens to kill them. Charley hums the overture, summoning the alien sentry, which grabs Hammond, but falls over the roof with him, eight stories up. The alien hits the ground and dies, but Hammond is clinging to the minute hand of the clock on the face of the building; he has four minutes until it reaches a vertical position and he falls to his death...

Cast

 * Charley Pollard - India Fisher
 * Hilary Hammond - Michael Maloney

Continuity

 * Charley refers to the "bats" in the TARDIS. (TV: Doctor Who)
 * The Doctor tells Charley that he has met William Tell. After successfully using a Sevateem crossbow to sever a length of rope on Leela's unnamed planet, the Fourth Doctor credited Tell for his skill and added that he was a "charming man." (TV: The Face of Evil) The Seventh Doctor once told his companion Ace that he had met Tell, though she believed that he may have been joking. (AUDIO: The Settling)
 * The Doctor has a penchant for kissing his companions on the lips when excited. Shortly after his seventh regeneration, he kissed Grace Holloway in San Francisco on 30 December 1999. (TV: Doctor Who) The Eleventh Doctor later did the same to Rory Williams and Jenny Flint. (TV: Dinosaurs on a Spaceship, The Crimson Horror)
 * Charley tells Hilary Hammond that she previously posed as a boy, Simon Murchford, aboard the British airship R101 in October 1930. She also notes that, according to the Web of Time, she should have died when it crashed in northern France. (AUDIO: Storm Warning)
 * The Eleventh Doctor refers to the fact he has sent messages to several of his other incarnations. (AUDIO: The Time Machine)