->''You know how it is. You put things off for a day and before you know it it's a hundred years later.''
-->-- '''The Doctor'''
Traveling alone together ([[CelibateHero with none of that, thank you]]), the Doctor and Nyssa are interrupted in their travels by a random alien force that tries to take over the body of the Doctor. The Doctor is perturbed, sure, but the Time Lords are ''completely freaked out'' by this. Worried that it might happen again, which would be bad news as the alien is made of anti-matter, the Time Lords decide to drag the Doctor back to Gallifrey and ''kill him''. With a token show of regret, Lord President Borusa gets Creator/ColinBaker to shoot the Doctor and haul him off to the Disintegration Chamber. But someone has conveniently rigged the circuit so that he ends up just being shoved into the Matrix ([[Film/TheMatrix no, not that one]]) where the anti-matter alien torments the Doctor... revealing that he's the long-lost (and allegedly dead) Time Lord [[Recap/DoctorWhoS10E1TheThreeDoctors Omega]].
Meanwhile, in [[SceneryPorn Amsterdam]], a pair of English teenagers are menaced by a humanoid chicken with a label-gun. ...[[NotMakingThisUpDisclaimer stop laughing]]! One of them is brainwashed, and he happens to be Tegan's favourite cousin, and Tegan happens to have lost her job, and happens to be visiting her cousin on this exact day. Then they all happen to be abducted by Omega, [[ContrivedCoincidence who wasn't actually aware that Tegan knows the Doctor at all]].
As it turns out, the Doctor [[NotQuiteDead isn't dead]]. Omega brings the Doctor back and starts making a copy of the Doctor's body for himself. So the Doctor, Nyssa and the TARDIS run down to Amsterdam, to try and stop him, but they're too late. Omega sheds his massive helmet to reveal... [[MirrorMatch the Doctor]]! In a most surreal scene, the Doctor and Omega-in-the-Doctor's-body banter back and forth before the Doctor reveals the big problem with Omega's plan: the body is only temporary.
Omega then leads the Doctor on a merry chase throughout Amsterdam, though he does take time out of his busy schedule to watch a Dutch street organ and test out his Villainous Creepy Smile on a little kid. The Doctor and Nyssa try to track him down, Creator/PeterDavison tries to speak Dutch and gets three out of three words wrong, and they freak out a lot of people around the Amsterdam grachten. Alas, Omega's antimatter body is dissolving, shown to truly gross effect by its face and hands dissolving into paste and green Rice Krispies. Eventually, Omega degrades to the point that he's a completely different actor, and the Doctor calmly (if reluctantly) takes out that label-gun and shoots Omega. Omega then fades to dust, and everything is back to normal.
...oh, and Tegan joins them again. The Doctor tries to put on a happy face, but it looks like he'd rather have [[TheScrappy Adric]] back.
This serial is notable in three ways. The first of which is that this features the return of [[Recap/DoctorWhoS10E1TheThreeDoctors Omega]], who last appeared in the 10th anniversary special. The second is that this serial kicks off the 20th anniversary season of Doctor Who. The final? Sixth Doctor Creator/ColinBaker shows up for the first time in the franchise -- not as the Doctor, but as JerkAss security chief Maxil. In fact, there's even a scene of Maxil ''shooting'' the Doctor, something that's caused a lot of jokes within the fanbase and cast. Colin Baker himself joked that he'd gotten the part of the Doctor by [[Main/KlingonPromotion shooting the incumbent.]]
* ActingForTwo: Peter Davison as the Doctor and Omega.
* AntiVillain: Omega, when he has the Doctor's body... just goes around enjoying having a body again and smiling at people. Okay the smile is ''creepy'', but the guy's only company for the past million years have been monsters made of red bubble wrap in an anti-matter dimension... he's a bit out of practice with social interaction.
* BewareTheNiceOnes: Nyssa shoots an awful lot of people in this episode, and even pulls a gun on the Lord President Borusa.
* BodyHorror: The slow degeneration of Omega's new body.
* CombatPragmatist: [[Creator/ColinBaker Maxil]].
-->'''The Doctor:''' Hello, I'm the Doctor.
* ContrivedCoincidence: Tegan being in the plot at all.
* HamToHamCombat: Omega and the Doctor lob large roasts back and forth with glee as they devour everything in sight (not even Amsterdam is spared), even while Creator/PeterDavison plays off himself. Colin Baker does his absolute best to join in the fun.
* HeyItsThatGuy: [[Film/BatMan Alfred]] (and [[Recap/DoctorWhoS3E7TheCelestialToymaker the Celestial Toymaker]] ) betrays Gallifrey to Omega.
* ItsAllAboutMe: Maxil is positively bored with the Doctor, and spends much of his screentime looking mildly offended or checking his nails. JohnNathanTurner actually asked Creator/ColinBaker to tone it down, because the show was called ''DoctorWho'' and not ''Commander Maxil''. Baker replied that no person would ever consider themselves a minor character in someone else's life, and so he played Maxil as someone convinced he was the main character of the story. Of course, Baker soon would ''become'' the main character, making the whole thing quite HilariousInHindsight.
* JustFollowingOrders: Maxil.
* MirrorMatch: A lovely scene where Peter Davison plays the Doctor ''and'' Omega -- with the latter dubbed by Ian Collier, of course. This was so well done that many on the DVD commentary remarked that the voice fit Davison ''better'' than his own!
* NotEvenBotheringWithTheAccent: Marvel as Creator/PeterDavison struggles to pronounce "Jeugdhotel Centraal".
* TheOtherDarrin: Ian Collier replaces Stephen Thorne as Omega.
* ReverseThePolarity: Nyssa claims it's the way to turn matter into antimatter.
* SceneryPorn: About a third of this adventure is in Amsterdam. Literally, this was ''the reason'' for the script being written. The script is able to HandWave it away, luckily, but it still feels damned strange.
* SealedEvilInACan: Omega.
* ShownTheirWork: Everything about Amsterdam checks out: the scenery, the street organ, the clothes. The background music is indeed a very popular Dutch tune about Amsterdam. The Dutch people are played by Dutch actors using their regular Dutch accents. And although the city is actually two meters ''above'' sea level, its cellars are indeed a bit below. The only thing that's off is Creator/PeterDavison's truly atrocious prononciation of Dutch, but luckily, he only gets three words ("Jeugdhotel", "Centraal" and "Frankendael").
* UnusuallyUninterestingSight: Averted. Watch when Peter Davison in monster makeup is staggering through Amsterdam in part 4: most of the citizenry barely notice, but there's a pair of people in one shot who outright goggle at the bizarre sight. Davison, on the DVD commentary, speculates that they ''weren't'' extras, and that it must have made for a weird holiday experience.
* WoobieDestroyerOfWorlds: Poor, screwed up, crazy Omega....