[[quoteright:345:http://static.tvtropes.org/pmwiki/pub/images/math_badge_8760.jpg]]
[[caption-width-right:345:[[{{Hamlet}} The rest...]] [[SilentCredits is silence.]]]]
-> ''[[FamousLastWords Now I'll never know if I was right.]]''
-->-- Adric

One of the biggest {{Wham Episode}}s that ever happened on ''Doctor Who'''s classic series.

A bunch of people who look like they bought surplus helmets from ''Film/StarshipTroopers'' go into a cave system to find a bunch of palaeontologists who have gone missing. They're also followed by a pair of shadowy figures who look like people in costumes.

Meanwhile, in the TARDIS, the Doctor and Adric are having a rather childish argument. Adric feels that he's being bullied, ignored and treated like an incompetent underling, and wants to go back home to E-Space. But the Doctor thinks it's too dangerous as E-Space is... E-Space. Either way, the Doctor materializes the TARDIS on [[TheFuture 26th century]] Earth in a cave system and goes out for a little sulk. Nyssa and Tegan join him, pointing out dinosaur fossils in the walls as they go. (As they discuss the fossil, we even hear the first xylophone riff from the "Fossils" movement of Saint-Saens' Carnival of the Animals.) The Doctor, who's read ahead in the script, mentions that he's always wanted to know how those dinosaurs died out.

Back with the missing-palaeontologists plot: the troopers decide to [[LetsSplitUpGang split up into multiple groups]] and explore deeper into the cave system. They even pick up a few life signs -- one of them with two heartbeats. The leader of this group naturally assumes that the owners of these strange life signs are responsible for the palaeontologists who went missing, but they don't have much time to act on this before they are, sadly, turned into sludge. The survivors, lead by a man named Scott, stumble across the Doctor and the TARDIS and immediately relate their problems... until, that is, they notice that the Doctor, Tegan and Nyssa make great suspects. Before either group can make their case, however, those shadowy figures attack: Androids! Androids commanded elsewhere in a distant location by... Cybermen!

Adric wanders out of the TARDIS and is nearly killed by one of the two Androids attacking everyone else, giving them a chance to take the Android out. The second one falls soon after, but the Doctor realizes that those who controlled the Androids were sending some sort of transmission to a hatch built into the cave. Opening the hatch, the Doctor is shocked to find a bomb has been set by whomever started this mess. Bravely, the Doctor takes the bomb out of its hiding place and fumbles around with it, luckily defusing the bomb before it can be activated. Ha ha, no. The Doctor actually ''activates'' the bomb with his fumblings and it takes the combined efforts of the Doctor and Adric together to turn the bomb back off again.

The Cybermen, for their part, finally put two (a TARDIS) and three (a man dressed oddly who meddles in their affairs) together and get five (the Doctor). They start preparing for his inevitable meddling as well, but not before the Cyber-Leader decides to show the audience some footage of the First, Second and Fourth Doctors from some of their Cybermen-oriented adventures.

The Doctor, satisfied with his deeds in the cave, ushers Adric, Nyssa and Tegan (as well as a few surviving humans from the cave) into the TARDIS. He decides to go trace the signal sent by the Cybermen to the Androids and the TARDIS materializes upon a freighter ship out in space that's suffered many random murders aboard during their travels to Earth. Almost immediately after stepping out of the TARDIS, the Doctor and Adric stumble across two dead bodies. Of course, the crew [[TheCorpseStopsHere finds the Doctor and Adric standing over the bodies]] and blames them for the murders.

The Cyber-Leader chooses ''now'' to take over the freighter, and activates a unit of Cybermen. They hatch from their tombs and begin to stomp all over the ship as the Doctor and Adric are taken to the Captain, a middle-aged woman named Briggs (hey, it's Beryl Reid!) who has the rare talent of sounding eternally drunk. One of the Cybermen bumbles onto the bridge and is instantly killed, only for the security chief to conveniently declare he's a double-agent for them. The Doctor and Briggs barricade the bridge by shutting the doors and Captain Briggs at first seems confident that they can survive to Earth... until she realizes that there must be around 15,000 Cybermen on the ship, hiding in her ship's cargo.

Meanwhile, the people stuck in the TARDIS decide to go see what happened to the Doctor and Adric, only to find a few Cybermen running around. Tired of waiting around, Tegan joins them and shows she TookALevelInBadass somewhere along the line when she kills a Cyberman with its own gun. Back on the bridge, the Cybermen nearly break through by melting one of the doors... until the Doctor manages to re-solidify said door around a lone Cyberman. Of course, the Cybermen just blow up the other door and take the bridge anyhow. Bragging, the Cyber-Leader activates all the remaining Cybermen on the ship, proudly announcing how he's won the day -- but not before [[YouHaveOutlivedYourUsefulness killing off the security chief]] under the mistaken belief that he attempted to hide the existence of Scott and his troopers, proving that bad communication really does kill.

Finally, the Cyber-Leader [[EvilGloating announces his plan]], which is so vast that it requires about 15,000 Cyber units. There is a massive meeting of governments taking place of Earth, which will unite all those peoples against the Cybermen. So the Cybermen have decided to break up the meeting, which makes sense. Turns out that little shoebox-sized bomb the Doctor deactivated in the caves was powerful enough to ''destroy everyone and everything on the planet's surface'', proving that the Cybermen firmly believe that ThereIsNoKillLikeOverkill. The Doctor thwarted their attempt to detonate the bomb, but the Cyber-Leader has a contingency plan -- crash the freighter into Earth, and the explosion of its antimatter-fuelled reactor will have basically the same result.

Regardless, Tegan is captured and dragged to the bridge while Scott and a few other humans run around blowing up Cybermen... but spending most of their time hiding from them. The Doctor makes a show of bravado until Tegan is threatened, and the Cyber-Leader claims that this is the weakness of organics. The Doctor claims otherwise, wondering when the Cybermen enjoyed the laughter of a child or sat down to have a nice meal together. The Cyber-Leader also heads out to the TARDIS to make his escape with a few other Cybermen. At this time, Scott's Commandos break onto the Bridge and pretty much slaughter most of the Cybermen there. Unfortunately, Adric's attempt to bring the freighter out of hyperdrive goes spectacularly wrong and sends the freighter careening back in time, meaning that the Earth of the future may be safe but the Earth of the past (and thus, all future) is now in danger.

Adric decides to stay at the control console, trying to fix the problem before everyone dies. Scott's Commandos and Captain Briggs instead leap out into escape pods, while the Doctor and the two ladies head out to recapture the TARDIS from the Cybermen. Inside the TARDIS, the Cyber-Leader holds the Doctor and companions at gunpoint while they talk for a good length of time. The Cyber-Leader brags about how Earth will be wiped out, but the Doctor then realizes that they've gone back in time just over 65 million years. This means that the dinosaurs were wiped out by the freighter/bomb combination rather than any meteor or asteroid... but no one remembers to tell Adric this, and he is feverishly crunching numbers in an attempt to stop the ship.

Fed up with the talking, the Doctor finally straight-up murders the Cyber-Leader by first rubbing Adric's golden badge all over it, but not before it shoots and damages the TARDIS console. And then the Doctor shoots it repeatedly in the chest with its own gun for good measure. Several times over. Adric, for his part, is nearly done screwing up history when a lone, near-death Cyberman prevents him from entering the calculations by blowing up the console. The Doctor knows he can't save Adric, and we watch Adric's ship ram itself into the surface of the Earth, killing off all the Dinosaurs and making way for Man... with Adric along for the ride.

Watch it [[http://www.wat.tv/video/classic-doctor-who-episode-3wnwx_3ka95_.html here]].(English with French subtitles.)

!!Tropes

* ActionGirl: Against all expections, ''Nyssa'' is the one who guns down the Cyber Lieutenant at the end of the story. Tegan is less successful in this regard, as she does manage to kill one Cyberman, only to be captured moments later and then spends the final episode being held hostage by the Cyber-Leader.
** Plus at least a third of the soldiers are female, instead of the [[TheSquadette usual token female guest star]] amongst an all-male battalion.
* ArtisticLicenseBiology: Dinosaurs are described as a "species". As in, just one.
* ArtisticLicenseGeography: Adric's ship seems to be heading straight for Korea, which apparently looks the same 65 million years ago as it did today -- as does the rest of the Earth, in fact (the remastered special effects on the DVD fix this mistake).
* BBCQuarry: One of the few serials of Doctor Who to feature a quarry ''that the Doctor and companions never visit.''
* BechdelTest: Passes with flying colours and a [[JustForPun gold star]].
* BoomerangBigot: The Cyber-leader mocks the doctor about emotion, but he seem to show traits of it himself.
* BittersweetEnding: The Cybermen are stopped but at the cost of Adric's life.
* TheCorpseStopsHere: at the Doctor's and Adric's feet.
* CreepyMonotone: Played straight (sort of), but ONLY by the regular Cybers. The Leader sounds, er... [[LargeHam very emotional]] at some bits, due to actor David Banks having a Cybermen obsession. (He would go on to write and record a four-hour comprehensive history of the species, just for the heck of it.)
* ADayInTheLimelight: Each of The Doctor's companions was given a story where they could take a bigger role this season. This is Adric's. He gets the HeroicSacrifice, the first since Katarina and Sara Kingdom back in season three.
* FamousLastWords: Adric's "Now I'll never know if I was right."
* {{Flanderization}}: In the olden days, the Cybermen didn't have a specific weakness to gold. Their inner mechanisms were simply clogged by dust, and since gold doesn't corrode it was tougher for them to flush out of their systems. Any dust thick enough would've done the job--''lead'' dust would have worked just as well, and been cheaper too. But by the time this serial rolled around, ''gold itself'' acted on them pretty much like Kryptonite. After this it would get even worse, leading to jokes that eventually just shouting the word "gold" at them would kill them.
* {{Flashback}}: The Cyberleader gives his lieutenant a brief history of their encounters with the Doctor. Clips from "[[Recap/DoctorWhoS4E2TheTenthPlanet The Tenth Planet]]", "[[Recap/DoctorWhoS5E7TheWheelInSpace The Wheel in Space]]" and "[[Recap/DoctorWhoS12E5RevengeOfTheCybermen Revenge of the Cybermen]]" are shown, though the Cyberleader mentions the events depicted in "[[Recap/DoctorWhoS5E1TheTombOfTheCybermen Tomb of the Cybermen]]" rather than Wheel.
* {{Foreshadowing}}: The Doctor while looking at dinosaur fossils says he always meant to go back and find out what killed them.
* HamToHamCombat: Whenever the 1980s version of the [[LargeHam Cyber-Leader]] is involved, expect wall-to-wall scene chewing from ''at least'' one other actor. Such as Creator/PeterDavison in this serial, who tries to out-ham his enemy with all he can muster.
* InformedAttribute: The Cybermen are supposed to be emotionless. It is not apparent.
* KilledOffForReal: Being blown to shreds and scattered across the prehistoric Earth will do that to you. (Although the BigFinish audio "The Boy That Time Forgot" gave Adric a different fate in the end.) Incidentally, this was the third and final instance of a classic series companion being killed, unless you count Kamelion, and Peri's death-that-wasn't.
* LargeHam: The Cyber-Leader, of all people. "My army awaits, DOCTORRR!" Throughout the episode, he displays anger, pride, irritation, even malicious smugness. It's even Lampshaded by the Doctor:
--->''Compared to some, this one is positively flippant.''
** Even a ''single word sentence'' from the Cyber-Leader becomes hamtastic, thanks to how it's read out each and every single time.
--->''Excellent!''
* LeftHanging: The surviving crew members of the freighter escape in their lifepod but it happens after they time travel to prehistoric Earth. The last we hear of them is Lt. Scott informing the TARDIS crew by radio that Adric wasn't on the lifepod with them. They are promptly forgotten about in the wake of Adric's death, and their fate isn't revealed until [[Recap/DoctorWhoS19E7TimeFlight the following story]], where Nyssa mentions in passing that they returned the crew to their own time. This wouldn't have been so problematic at the time, since stories in this era often used the first episode of the following serial to tie up any loose ends, but with the VHS and DVD releases of this story and "Time-Flight" being separated by several years, it left more than a few modern-era viewers wondering WhatHappenedToTheMouse.
* LetsSplitUpGang
* MissingEpisode: The reason for the story mismatch in the flashbacks is that ''[[Recap/DoctorWhoS5E1TheTombOfTheCybermen The Tomb of the Cybermen]]'' had yet to turn up.
* PhlebotinumKilledTheDinosaurs: Turns out the ship that crashes into Earth (with Adric still on it) ''was'' the supposed meteor that killed the Dinosaurs.
* PlotDrivenBreakdown: The TARDIS' controls get damaged at the ''worst'' possible time...
* SealedArmyInACan: The Cyberarmy on the cargo ship.
* SensorSuspense: The expedition base camp has a scanner that shows life-signs moving around in the cave system the expedition is exploring. Over the course of the first episode we get dots suddenly disappearing (expedition members being killed), a dot that fades in and out (the thing that's killing them, which is alien enough to confuse the scanner), and dots suddenly appearing (the Doctor and friends arriving, just in time to be accused of the murders).
* SilentCredits: At the end of the last episode.
* TakingYouWithMe: Just before a Cyberman dies it shoots the controls, meaning Adric can't pilot the ship away.
* TrailersAlwaysSpoil: Averted to truly heroic levels. Showrunner Creator/JohnNathanTurner went to enormous lengths to keep the Cybermen's return secret, resulting in a famous OhCrap moment when Episode 2 aired. JNT actually avoided getting a cover shoot on the ''Radio Times'' in order to keep the secret as secret as possible, also insisted the cast listings in the same magazine simply referred to the Cybermen with speaking parts as "Alien Leader", "Alien Lieutenant", etc.
** Too bad there's a Cyberman on the DVD cover.
* WeaksauceWeakness: The gold. See 'Flanderization.'
* WhamEpisode: Companion death has always been very rare. "Earthshock" intensified the effect by silently rolling the credits over a picture of Adric's badge, smashed beyond repair. While that's the biggest WHAM part of the episode it also has further value: Back when it first aired, the Cybermen being the villains was a well kept secret which also adds to the shock value. But both twists have suffered ItWasHisSled at this point.
* WhyDontYouJustShootHim: When Briggs asks this the Cyberleader says he wants his guards to watch the reactions of the crew [[ForScience for scientific reasons]], so they can understand human weaknesses.
* YouHaveOutlivedYourUsefulness: Amusingly subverted. It appears that the Cybermen initially intend to honour their deal with Ringway, but when Scott's troopers arrive on the freighter and start shooting up the place, the Cyber-Leader wrongly assumes that these are extra crewmembers who Ringway was trying to hide the existence of, and kills him at the next opportunity.
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