30 October, 1938: one month after a fantastically bright meteor lit up the skies of New York City, a pair of two-bit hoodlums have stolen merchandise from their boss, Don Chaney, to sell to a third party. However, the man who arrives at the rendezvous is a private detective, J.C. Halliday, who tries to arrest them both. Ellis shoots him first, with a gun which, as odd as it may look, is even more effective than Halliday’s hand-me-down pistol... As Ellis and Mouse flee, the TARDIS materialises nearby, and the Doctor emerges, still telling Charley about his encounter with the legendary King Canute. On that occasion, he managed to stop an amoral Time Lord with an alien flood controller from convincing Canute that he had in fact turned back the tide; but he knows that messing about with History can be a dangerous business. He and Charley soon realise that this isn’t Singapore in 1930; they’ve arrived in New York City, near a very dead body. The Doctor searches the body, learns that the dead man was a private detective, and decides to investigate -- for Halliday has been fried to a crisp, in a manner which has no place in Earth of the 1930s.

Elsewhere in the city, at the CBS studios, Orson Welles and John Houseman are in rehearsals for the Mercury Theatre’s forthcoming Hallowe’en broadcast. Welles isn’t terribly interested in this sci-fi garbage, but his sponsors insist upon presenting a Hallowe’en special, even though Welles is sure that everyone will be listening to the popular ventriloquist Edgar Bergen on a rival station. As the rehearsals continue, the receptionist Carla goes home for the evening, surprising network chairman Bix Biro on her way out. He seems nervous, and rushes her out of the office -- for the extra connections he’s wiring into the broadcast booth have nothing to do with entertainment...

Ellis joins the rest of Chaney’s men for a dinner out at Luigi’s, where Chaney notes that Mouse is missing and decides to do something about it. However, two would-be hit men then show up with a message for “the Phantom”. Chaney doesn’t appreciate this nickname, nor the fact that the gangsters draw attention to his nose having been shot off in the past -- and they discover too late that Chaney is armed as well, with an entirely different sort of gun. Moments later, the two men have been fried to a crisp. Meanwhile, at a rather more up-scale dinner elsewhere in the city, the flamboyantly effeminate gossip columnist Cosmo Devine trades witticisms with Mrs van Buren and amuses the crowd with his anecdotes, while asking them for donations to his theatre project. As soon as it’s convenient, however, he takes his leave of them to make an important phone call...

The Doctor takes Charley to Halliday’s office, hoping to learn how Halliday got himself killed by a concentrated blast of radiation. Just as they’re about to enter, a woman named Glory Bee arrives, and assumes that the Doctor is Halliday. To Charley’s despair, the Doctor decides to play along, and invites Glory into “his” office, where she explains that she’s trying to find her missing uncle. He was in the city for an important conference, but he’s disappeared from his hotel, and the address which he gave for the conference is just an empty warehouse by the East River. Charley privately insists that the Doctor stop playing around and hand the case over to the police, but the Doctor then learns that Glory’s uncle is an atomic scientist. If the real Halliday was killed by a radiation burst just as an atomic scientist has gone missing, perhaps there’s a connection...

Welles and Houseman wrap up rehearsals and send the rest of their company on their way to rest up for tomorrow. Welles, exhausted, decides to skip Devine’s fundraiser in favour of a private booth at the Excelsior Hotel, but as he and Houseman prepare to leave, they surprise Bix Biro on his way in. Biro seems flustered, and irritates Welles with his Philistine attitude towards Welles’ art; but while Welles knows that Biro has mob connection, he doesn’t know that Biro has very good reason to be worried. Cosmo Devine has kidnapped Biro’s lover, young Jimmy Winkler, and he’s ordered Biro to ferret out certain information and plant a secret signal in tomorrow’s broadcast. If he fails to do so, then Winkler will meet an unpleasant fate...

Charley wakes the next morning in Halliday’s office, to find that the Doctor has worked through the night. It seems that Halliday’s final investigation involved the Excelsior Hotel, where Glory’s uncle was supposedly staying before his disappearance. The police arrive, having found the real Halliday’s body, and when the Doctor and Charley flee down the fire escape, Charley is kidnapped by a thug who has been waiting outside. By the time the Doctor realises she’s no longer behind him, there’s no sign of her anywhere. Glory then arrives to inquire as to the progress of the investigation, and the Doctor, realising that he’s in too deep, must abandon the search for Charley and accompany Glory to the Excelsior. Meanwhile, back at CBS studios, Bix Biro tests Carla’s new dictation-recording machine, and receives a call informing him that the attempt on Chaney’s life has failed.

Welles and Houseman are just leaving the Excelsior as the Doctor and Glory arrive; Houseman had checked Welles in to sleep off the excesses of the previous night. Ellis and Cosmo Devine are also here, meeting secretly in the lobby so Ellis can explain why Cosmo’s agent found a dead body at the rendezvous, rather than the guns which Cosmo planned to purchase from Ellis. Ellis explains about Halliday, and informs Cosmo that his men have already spotted a man and a woman snooping around; they’ve kidnapped the woman and taken her to Cosmo’s house in New Jersey for further questioning. Devine is interested in learning the source of these weapons, but Ellis won’t betray Chaney to that extent. They then overhear the Doctor and Glory at the front desk, inquiring about the missing Yuri Stepashin; Cosmo has his own reasons for wanting to meet the missing Professor, and Ellis knows where he is. The Doctor and Glory get nowhere with the desk clerk, and Glory thus pretends to faint, giving the Doctor the opportunity to check the guest register. There, he finds a clue which leads him and Glory to room 1504 -- where another of Ellis’ thugs is waiting for them...

Stepashin is in fact in the lair of the Phantom, trying to work out what keeps the alien in the tank alive. While delighted by the opportunity to study alien technology, he’s repulsed by Don Chaney’s intentions to sell the alien technology to the highest bidder; however, Chaney assures him that the Nazis aren’t even welcome to bid. He feels sure that the CIA will pay his price, eventually. As Stepashin resumes his work, Chaney returns to his office to listen to Bergen’s radio show; unfortunately, one of his goons spoils the illusion by pointing out that, on radio, you can’t tell whether the ventriloquist is moving his lips or not. Irritated, Chaney changes stations, but then gives up on the radio and takes his leave, thus missing the opening of one of the most infamous radio dramas of all time. Welles may consider the production as a whole beneath him, but even he has conceded that the introduction is very well written indeed. We now know that in the early years of the 20th century, this world was being watched by intelligences greater than Man’s, and yet as mortal as his own... History is being made.

Charley has been imprisoned in Cosmo’s house in New Jersey, along with Jimmy Walker, Bix Biro’s boyfriend. Winkler has been here for three weeks, and he’s learned that Cosmo is arranging for the German army to invade the United States. Cosmo has learned about the alien spaceship which crashed in New York City last month, and he knows that it’s been found by mobsters -- and thus, he kidnapped Winkler in order to blackmail Biro into using his underworld contacts to find out where the ship has been hidden. Cosmo himself then arrives, and questions Charley about her interest in Stepashin. Dissatisfied with her answers, he prepares to administer a drug which will force the truth out of her -- and as they struggle, The War of the Worlds continues to play on a nearby radio...

Ellis visits Cosmo to find him questioning the drugged Charley as Winkler watches, helpless to intervene. However, none of them can make sense of Charley’s ramblings about King Canute and time machines, and Cosmo eventually gives up and returns to the radio, waiting for the signal he’s expecting. They’re interrupted by the sound of something loud passing by overhead, but are unaware that the object has embedded itself in the fields nearby. Incredible as it may seem, strange beings have indeed landed in the Jersey farmlands -- Destroyer Streath and Conserver Noriam, two giant, bat-like aliens who have come to locate their lost breeding party and quite possibly blast this entire world to dust...

Somewhat too late, the Doctor realises that Stepashin was attempting to defect, to escape a future of gulags and prisons. Now “Glory Bee” will be returning to the USSR with a bonus -- alien technology which has already enabled the Professor to begin work on a prototype atomic weapon. Glory forces Stepashin and the Doctor out of Chaney’s lair at gunpoint, and they’re all surprised to find that the hideout is in fact inside a leg of the Brooklyn Bridge. Chaney catches them and pulls one of the alien weapons on Glory, resulting in a stand-off. The Doctor urges him to see reason and destroy the alien technology rather than let the human race destroy itself with technology it isn’t ready for yet, but Chaney has already made a deal with the CIA, and he suspects that the Doctor is just trying to get hold of the spaceship for Great Britain. Before the stand-off can be resolved, a panic-stricken gangster arrives, claiming that the radio has just reported a Martian invasion of New Jersey. At first, the Doctor assumes that the owners of Chaney’s ship have returend for their lost property -- but he then remembers that the date is 31st October, 1938, and bursts out laughing as he realises the truth...

Bix Biro has sent out the coded signal, embedded within Welles’ broadcast, informing Cosmo that he has the information Cosmo requires -- which means that there’s no further need for Cosmo to keep Ellis alive. Charley is beginning to recover, however, and she attacks Cosmo and holds him off while Ellis hits him with a chair, knocking him out. In the scuffle, however, Cosmo’s gun goes off and Winkler is killed. Charley and Ellis flee from the house, only to run into Streath and Noriam outside. The aliens are still surveying the planet upon which they have landed, and they question Charley and Ellis about their world’s defensive capabilities. Ellis, unsure what they mean, claims that all of their weapons are in the city. Streath and Noriam conclude that the lost breeding party must have crashed in the city, and decide to take Charley and Ellis with them while they investigate.

Carla and Bix are the first to learn what Welles has done to America, as the switchboards light up and panic-stricken mobs riot in the streets. Infuriated, Bix orders Houseman to write an apology to the country; he’s expecting an important visitor, but he’s going to have some choice words for Houseman and Welles afterwards. Cosmo then arrives, having recovered and made his way through the mobs outside; fortunately, nobody recognised him as he entered the studios. As “requested”, Bix confirms that Chaney got to the alien ship before the CIA could, and reveals the location of his lair. Satisfied, Cosmo shoots Bix dead and departs, unaware that their entire conversation has been recorded on Carla’s new dictation machine...

The stand-off on the Brooklyn Bridge is broken when Streath and Noriam’s alien ship arrives, distracting Chaney for a moment. Glory tries to take advantage of the distraction to grab the Professor, but Chaney’s thug shoots at her, blowing out part of the bridge and causing her to fall to her death. Noriam detects the energy discharge, proof that the aliens’ weapons are being used, and he and Streath prepare to land and reclaim their lost property. Ellis blames himself for this situation; he was a fool to try to sell out his boss, and somehow he must make good. But he and Charley fail to hear a brief, petty argument between their captors, which suggests that they may not be the invincible warlords they claim to be...

Cosmo flees in terror as the aliens tear apart the German soldiers. The Doctor and Chaney are close behind, but Stepashin lags behind, overawed by the magnificent alien monsters, and he is overwhelmed. The Doctor worries what the adults will be like if the children are so savage, and he soon gets a chance to find out, as Streath and Noriam break in, in search of the missing breeding party. The Doctor and Charley are finally reunited, and it’s a much happier reunion than the one between Chaney and Ellis when Chaney realises that Ellis is the one who’s been selling him out. Noriam questions the Doctor and Cosmo, both of whom claim to speak on behalf of Earth, but the Doctor soon realises that Noriam’s claim to be spearheading an alien invasion is just empty bluster. Streath and Noriam aren’t alien warlords -- they’re alien criminals running an elaborate protection racket. They release breeding parties on primitive planets, allow the savage children to wreak havoc, and then offer to protect the devastated worlds from further “invasions” -- for a price. Their third partner was killed when his ship crashed on Earth, but it appears that the breeding party wasn’t destroyed after all -- their gestation was merely delayed.

Cosmo decides that the aliens are his ticket to the high life now that the Nazis are out of the running, and tries to convince Noriam that his technology is so far in advance of Earth’s that he can easily conquer the planet. However, the Doctor claims that Earth has already been invaded; even now, an army of Martian war machines is marching towards the city, and Streath and Noriam had better get out while they can. Noriam suspects that the Doctor is bluffing, but before he can question him further, the savage hatchlings arrive. In the ensuing confusion, the Doctor, Charley and Chaney escape, while Noriam transmits a calming signal which subdues the hatchlings. Ellis remains trapped, while Cosmo remains of his own free will, still trying to convince Streath and Noriam that they’re more powerful than they think. They may not have the firepower of a full invasion force, but with Cosmo on their side to instruct them, a few well-judged strikes will enable them to conquer the world. Ellis is disgusted by Cosmo, but Cosmo doesn’t care; he simply guns down Ellis with his radiation gun and prepares to discuss terms with his new allies...

Welles and Houseman are now fully aware of what they’ve done, but when they enter Biro’s office to accept his lecture, they find him dead. What’s more, they find the dictation machine, which has recorded the entire murder -- and Biro’s claim that a real alien spaceship is hidden in the Brooklyn Bridge. Meanwhile, the Doctor, Charley and Chaney are on their way to CBS studios in Chaney’s ’29 Lamborghini, for the Doctor has a plan to get rid of the aliens. It’s going to require a bit of acting, however -- and the TARDIS. Back in Chaney’s hideout, Streath and Noriam pack up the remains of the technology from the lost ship, including the hatching tank and Professor Stepashin’s experiments.

Chaney’s men bring the TARDIS to CBS, and Chaney himself uses his connections within the police to get himself, the Doctor and Charley into the studios, past the angry mob outside. There, Welles is trying to report Biro’s murder to the CIA, but they hang up on him -- even if he is the real Welles, they’re infuriated by what he’s just done. The Doctor offers his help, but Welles is confused by the Doctor’s claim to have enjoyed all of his films; he hasn’t made any yet. Oddly, Welles doesn’t seem to recognise a quote from Hamlet which the Doctor makes while outlining his plan to get rid of Streath and Noriam. As the other actors have gone home already, and won’t be able to get back through the angry mob outside, the Doctor, Charley and Chaney are going to have to play extra parts for the new production -- a very special re-broadcast of The War of the Worlds, for a very select audience. Welles and Houseman agree to play along, and as the performance begins, the Doctor wires up the TARDIS to the broadcast booth and locates the frequency he needs.

Despite handing over his gun as a gesture of good faith, Cosmo has still been imprisoned in the aliens’ cargo hold. There, he seems to hear movement from the hatching tank, but before he can investigate, Noriam arrives to question him about the Earth’s weaknesses. Cosmo accompanies Noriam to the bridge, where he outlines the current political situation; in his opinion, a few quick strikes against the States, the Soviet Union, France, England, and Germany will leave the remaining countries lost and leaderless. However, as he negotiates for his own seat of power, Streath picks up the Doctor’s broadcast -- and realises that it seems to be reporting a genuine alien invasion. He and Noriam have heard of the legendary Martian warriors before, and they conclude that Cosmo has been trying to distract them while his real allies attack. Streath drags the protesting Cosmo back to the cargo hold to await his long and painful death, while Noriam launches the ship into orbit.

While the Doctor chews the scenery as the voice of the Martian warlord, Charley monitors the alien ship in the TARDIS, and soon reports that they’re on the run. The Doctor and his friends congratulate themselves on a successful performance... and realise too late that they’re still broadcasting. Streath and Noriam are infuriated, and turn their ship back around, intending to destroy the entire city for this humiliation. However, in the cargo hold, Cosmo hears movement in the hatching tank again, and Professor Stepashin emerges. Although he managed to hide out and survive the hatchlings’ attack, he’s been badly injured, and will soon be dead -- but as the aliens were kind enough to bring his experiments on board their ship, at least he can die saving the world. Is Professor Stepashin the first man in history to build a working atomic bomb? The answer, as Streath and Noriam soon find out, is yes.