Martha: What'd he do?The Doctor, wary of getting too attached to another human, or perhaps of getting another human killed, drops Martha off back home. Her time in the TARDIS is over. However, from the news on her TV he realises that Martha's time period is in danger, and returns only seconds after he left for — ostensibly — one more adventure with Martha.The activity in question is that of Dr. Richard Lazarus (Mark Gatiss), a brilliant elderly scientist who has devised a way to reverse the aging process. The scientist tests his equipment on himself at a black tie affair, which Martha and the Doctor attend as her sister is Lazarus's Public Relations director. When Things Spin, Science Happens, and Lazarus successfully turns himself into a young, healthy, 41 year old. Martha's sister is happy to see her boss now looking very young and handsome and snoggable indeed.Meanwhile, Martha's mother is approached by a suit-wearing guy, who hints that the Doctor is dangerous. He's 100% right about that (heck, he could even have added that the Doctor has a history of absconding with young women, sometimes kidnapping them(!), and that they don't always come home, oh and the Doctor killed Martha's cousin Adeola). This involves The Doctor getting smacked by his companion's mother (again).Then Lazarus surprises everyone by turning into a massive scorpion/lizard monster! Martha's sister laments that she was about to snog him and then runs for her life with the rest.The Doctor kills the scientist with the polarity-reversed age-reversal machine. However, the scorpion beast turns out not to be dead after all and flees to a cathedral, where the Doctor kills it again with an organ.With the day saved, The Doctor offers Martha yet another "one more trip". Martha says no to the "one trip" thing and The Doctor says "ok" while jerking his head at the blue box.But as the TARDIS takes off, Martha's mum leaves a message on the answering machine not to be with the Doctor, saying the notice came from Harold Saxon...
The Doctor: Changed what it means to be human.
The Doctor: Changed what it means to be human.
- Arbitrary Skepticism: During their final confrontation, Lazarus tells the Doctor about the Blitz. The Doctor mentions in reply that he'd seen it first hand. Lazarus dismisses this, pointing out that the Doctor looks far too young to have been there, and Doctor parries by pointing out that Lazarus looks too young himself. At this, Lazarus chuckles.
- Arc Words: Lazarus's experiment has some involvement with Mr Saxon, and the man who warns Martha's mother about the Doctor is revealed to be working for him as well.
- Big Red Button: The one on the aging reverser is pressed with an unusual lack of ceremony.
- Body Horror: Lazarus's transformation into an "evolutionary reject".
- Chekhov's Gun: During the conversation on the roof, Lazarus talks about how, during the Blitz, he and his family took refuge in the cathedral. The final confrontation is right there.
- Compliment Backfire: Martha, when she sees the Doctor in his tuxedo, says he looks like James Bond. The Doctor disgustedly replies, "James Bond?!", then thinks for a moment and says, somewhat less disgustedly, "Really?"
- Continuity Nod:
- The Doctor muttering to himself over being slapped by his companion's mother.
- The Doctor complaining that something bad always happens when he wears a tux.
- The Doctor saying "Really shouldn't take that long just to reverse the polarity. I must be a bit out of practice." Reversing the polarity was something the Third Doctor did quite often.
- Death by Irony: The Doctor weaponizes the device Lazarus built to achieve eternal youth. It doesn't take, and Lazarus is instead killed by the organ in the church where he sought shelter from the Blitz.
- Death by Mocking: The woman who rebuffs the Doctor's warning by stating the the greatest danger at the party is choking on an olive is one of the first people Lazarus kills moments later.
- Delayed Reaction: The Doctor sees Lazarus's press conference without commenting, leaves in the TARDIS, and then comes back to double-check what he just heard with Martha.
- Digging Yourself Deeper: The Doctor puts his foot in it talking to Martha's mum and gives her the impression that he's sleeping with her.
- Dirty Old Man: Pre-transformation Lazarus is implied to be this, what with his reaching for Martha's sister and asking her about the perfume she's wearing (it's called "soap".)
- Dying as Yourself: Averted as Lazarus was always himself, even while transformed.
- Follow the Chaos: Martha finds the Doctor by running towards the sound of the explosions.
- Fountain of Youth: Lazarus's machine is for rejuvenation.
- Game Face: Early on in Lazarus's mutation, his face changes to match his new form.
- Gone Horribly Wrong: Lazarus's machine works by reprogramming DNA and commanding it to rejuvenate. The problem is that he accidentally released a bunch of "junk" DNA that had been inactive until then.
- Handsome Lech: Post-transformation Lazarus appears to be this such as his attempts to charm Martha's sister, although he might just be trying to lure in easy prey.
- I Kiss Your Hand: Martha lets Lazarus do this for the sake of a DNA sample.
- Immortality Seeker: Having barely survived the Blitz as a child, Lazarus has been obsessed with conquering death all his life. He's looking forward to what he can accomplish in two, three or maybe four life times.
- Insult Backfire:The Doctor: "A science geek?" What's that mean?
Martha: Means you're obsessively enthusiastic about it.
The Doctor: (happily) Oh, okay!
- Innocent Innuendo: The Doctor causes a few awkward moments talking to Martha's mother by saying he and Martha haven't had much time to talk as they've been "busy". Fortunately, their conversation is interrupted before he can dig himself deeper.Francine: Busy? Doing what, exactly?
The Doctor: Oh... you know... stuff.
- Involuntary Shapeshifting: Lazarus constantly shifts between that... thing and his youthful human form due to an Unstable Genetic Code.
- Irony: The Doctor condemns Lazarus for doing whatever he can to avoid death. Funnily enough, he'll got on to do pretty much the same thing (only without turning into a hideous monster).
- Liquid Assets: mutant!Lazarus feeds on Life Energy.
- Living Forever Is Awesome: Lazarus thinks so. The Doctor disagrees.
- Loud of War: Sonic screwdriver plugged into cathedral pipe organ = weaponized music.
- Mad Scientist: The classic story of a deluded scientist who ends up turning himself into a monster.
- Meaningful Name: In the Bible, Lazarus was the man raised from the dead by Jesus. Which the Doctor neatly lampshades at one point; "I should have seen that coming."
- Monster Sob Story: Lazarus ruthlessly murders others to prolong his life, but you can somewhat sympathise with his sheer determination to conquer death.
- Never Be Hurt Again: Lazarus wants to avoid death because of his experiences during World War II. Waiting helplessly for bombs to blown him up, he vowed to never be so helpless again.
- No Immortal Inertia: Lazarus inexplicably turns back into an old man immediately after his death.
- Noodle Incident: The Doctor says he's seen something like Lazarus' tech before. His wording strongly suggests what Lazarus did isn't far removed from regeneration.
- No Transhumanism Allowed: Averted. The Doctor isn't against Lazarus' work per se but saying that he doesn't understand what he's dealing with. The immortality-is-bad thing is separate, applying to non-transhumans, such as himself
- Offscreen Crash: The ambulance carrying the apparently deceased Lazarus drives away from the reception gallery. Just after Francine slaps the Doctor, and the conversation that results, we suddenly hear a loud crash. The Doctor, Martha and Tish rush off to investigate the noise and find the ambulance has gone off the road and crashed. They open up the back doors and find that Lazarus has killed the paramedics by draining them of their life energy and escaped.
- One-Winged Angel: Lazarus transforming into a giant scorpion for battle scenes. There is no battle when he's human.
- Professor Guinea Pig: Lazarus' first success is himself. It's justified in that he's 76 years old and might not live long enough for clinical trials.
- Reverse Polarity: Mentioned by name when weaponizing Lazarus's device. The Doctor says "Really shouldn't have taken me so long to reverse the polarity. I must be out of practice."
- "The Reason You Suck" Speech:The Doctor: You can't control it, the mutation's too strong. Killing those people won't help you. You're a fool. A vain old man who thought he could defy nature, only nature got her own back, didn't she? You're a joke, Lazarus! A footnote in the history of failure!
- Seeking Sanctuary: As a child, Lazarus hid from bombs in a church. When he's losing control of his mutation, he retreats there a second time.
- Smash Cut: "The biggest danger here is choking on an olive." Smash Cut to the monster breaking into the room.
- This Was His True Form: After dying, (both times) Lazarus returns to human form.
- Unstable Genetic Code: Lazarus has one due to his experiment and it causes his mutation. Yes, Martha the medical student points out the sheer impossibility of this trope.
- Up to Eleven: The Doctor invokes it by name when dialing up the volume on the organ.
- When Things Spin, Science Happens: Lazarus' machine works by spinning really fast to create "hyper sonic resonance."
- Who Wants to Live Forever?: The Doctor informs him that being immortal in a world of mortal things is not fun at all. All you do is watch things waste away.The Doctor: I'm old enough to know that a longer life isn't always a better one. In the end, you just get tired; tired of the struggle, tired of losing everyone that matters to you, tired of watching everything you love turn to dust. If you live long enough, Lazarus, the only certainty left is that you'll end up alone.
- Your Princess Is in Another Castle: Lazarus is carted away in an ambulance... and there's almost 15 minutes left of the episode; just enough time for another climatic showdown...