The Sixth Doctor and Peri arrive at the Museum of Aural Antiquities, where they immediately stumble on a murder case. They're found standing over the corpse, but are quickly dismissed as harmless bystanders because no one would possibly commit murder in that coat.The museum's curator, Gantman, is a blind man who has also lost his sense of smell, meaning that all he has left is his hearing. He's anxious to solve the case, because today is an important day in the museum's history: the speeches of presidential candidate Visteen Krane will be broadcast. Krane committed suicide just before the elections, and his running mate, Beth Pernell, is jumping at the chance to let the public hear Krane's speeches praising her and convince his voters to vote for her now. She is helped by a producer named Hans Stengard. The only problem is that the speeches are being subtly altered by someone, and with no scripts and no video recordings to back them up, sound and memory are the only evidence.Meanwhile, the Doctor realises that the soundproofed museum is housing its own kind of ghost. The ghost, taking the form of crazed whisperings, attacks an intruder, Amber Dent. The Doctor eventually comes to a shocking revelation: The creature is actually a person who cheated death by using a frequency modulator to channel their brainwaves into audio wavelength. That's right, the homicidal creature is a Not Quite Dead Visteen Krane. Krane now exists as a living sound wave, able to mimick anyone in the museum and to broadcast himself using any sound that leaves the place.The Doctor tries to trap Krane by fiddling with the sound output, by trapping him on a CD, and by transforming the wave. He notes that if it was possible to predict what sound Krane would be hiding in, they would be able to use a wave cancellation to defeat it. Pernell steals the wave and tries to outright murder Krane by editing the wave in a crude editing program, deleting bits of it and interrogating a copy of the wave with the sound output unplugged. She never expected Krane to live on in any way, and him being present inside the speech seriously messes up her plans.The Doctor checks the speech again to see if Krane has altered it any more only to find that he hasn't. He then realises what this means: Krane intends for the speech to be broadcasted unedited, meaning that he would be able to hide in its audio, and since it would be played around the nation, his form would be duplicated: If the speech were to be broadcast, Krane would be in every home on the planet. Pernell still believes that she has won, unaware of the real danger. The Doctor tries to cancel the speech's broadcast, but is stopped by Krane.The Doctor convinces Krane to let him cancel the speech by telling him that it would essentially complete Pernell's plan for her - everyone would indeed believe that he endorsed Pernell and vote for her. He lets the Doctor through, but Pernell holds him at gunpoint before he can do anything. Peri, Gantman and Berkeley quickly ready the wave cancellation, so that the speech is not broadcast. Krane eventually replays the audio of his suicide, which prompts the Doctor to realise the truth behind the situation: Pernell wasn't trying to talk him out of suicide, she was talking him out of his speech denouncing Pernell; When Krane said that there was a gun at his head, he meant it literally - someone really was pointing a gun at his head; and the "tsk, tsk, tsk" noise in the background isn't a mechanical sound at all - it's a very specific Verbal Tic, used by one Hans Stengard. Krane didn't commit suicide - he was murdered by Stengard, working for Pernell.Gantman talks to a young research student who has been heard throughout the episode, Miles Napton, only for it to be revealed as Krane all along. Krane reveals that, although he was driven mad by Pernell's torture earlier, the cancellation had a healing effect, restoring his sanity. Krane agrees to help the Doctor in taking down Pernell. The Doctor confronts Pernell and gives her one last chance to take back the speech. She doesn't take it, and the speech broadcasts. However, to her dismay she finds that the speech is being edited on the go by Krane, and now denounces Pernell and her ways. The creature, still being broadcast, then plays the audio of his death, altered to make it clear that he was murdered. Finally, Pernell holds onto the hope that the nation will forget eventually and let it slide, and that her becoming the nation's leader is worth the price of a man's life. The Doctor reveals to her that the broadcast was still going out live, and everything she said was heard by the nation, leaving her political career in ruins.Krane stays behind to help Gantman run the museum as The Doctor and Peri leave, offering to return in a few years to check on them. After the time travellers leave, Krane and Gantman prepare one final transmission...Making her escape and still planing her revenge, Pernell is driving along a road when she receives an voicemail from Stengard. She opens it to hear Krane's voice bidding her farewell, before a cacophony of noises erupts from the speakers, startling her so much that she drives off the side of the road and crashes into a ditch.
- Back from the Dead: Visteen Krane comes back after his murder in the form of a wavelength.
- Big Bad: Beth Pernell.
- Cold-Blooded Torture: Pernell manipulates Krane by editing his sound file.
- Continuity Nod: The last time the Doctor was caught standing over someone's dead body, it got him accused of being the murderer and led to a very exhausting time spent on the run from his unreasonable human captors. Good thing that this time, his loud outfit spared him the trouble of being wrongly accused again.
- Democracy Is Bad: Beth Pernell's view, though she's not above using it to gain power before discarding it. The Doctor doesn't agree.
- The Dragon: Hans Stengard to Beth Pernell.
- Engineered Public Confession: Beth Pernell gives one at the end of the episode, thanks to The Doctor.
- Heel–Face Turn: Visteen Krane by the end of the episode.
- Hypocritical Humor/I Resemble That Remark!: After the Doctor overreacts to Peri's suggestion that they leave:Peri: Don't shout Doctor! There might be-The Doctor: SHOUT?! I don't shout! People who have to resort to shouting to get what they want are merely demonstrating the inherent paucity of their argument! It's something that I never, NEVER-Peri: All right Doctor!Doctor: Point made, I think.
- Monster of the Week: A ghost of a person who lives on as a sound wave, who can transfer his consciousness into any other sounds around him. Subverted later on, when he pulls a Heel–Face Turn.
- Never Suicide: Krane's death may seem like a suicide, but there's more to it than that. He was actually shot point-blank by Stengard.
- Our Ghosts Are Different: Krane survives through transferring his consciousness into sound waves.
- Painting the Medium: Done beautifully. The entire episode is an homage to radio, and it shows: Gantman is a blind man who only retains his hearing, the Museum is filled with aural exhibits, the supposed Monster of the Week is a ghost who an transfer his consciousness through sound, and the episode puts a huge emphasis on audio editing and manipulating equipment.
- Sanity Slippage: Visteen Krane goes through some after his Cold-Blooded Torture.
- Verbal Tic: "Tsk, tsk, tsk" is Stengard's, which is useful in unmasking him as Krane's murderer.
- Was It Really Worth It?: The Doctor questions Pernell as to whether her attempt to gain power was worth all the deaths. In her mind, it was.
- Wham Line: The caption above, where the Doctor reveals the identity of the soundwave ghost: "Is, or was, Visteen Krane!"