The Lazarus Experiment (TV story)

Synopsis
When the Doctor takes Martha home after her "one trip", he decides to stay around to witness the experiment of a man who claims to be able to "change what it means to be human".

Plot
The TARDIS materialises in Martha's flat. The Doctor tells her that they had agreed - one trip and home. It is about twelve hours after they left. Martha's phone rings, but she does not pick it up; it is her mother, Francine, saying that her sister Tish is on the news. Martha turns the television on and, alongside Tish, an elderly man, Professor Richard Lazarus, announces that tonight he "will change what it means to be human." The Doctor says goodbye to Martha and, oblivious to her upset, steps into the TARDIS. It dematerialises, but quickly rematerialises. "No, I'm sorry, did he say he was going to change what it meant to be human?"

At Lazarus Labs, Professor Lazarus and Lady Thaw discuss the need for the experiment to work, with Thaw mentioning that Mr Saxon is funding their research. Tish comes in and Lazarus attempts to flirt with her.

The Doctor and Martha attend Professor Lazarus' reception that evening, as do Martha's mother and her brother Leo. Martha introduces the Doctor to her family; Francine is suspicious of him. Lazarus announces he is to perform a "miracle", and steps into the manipulator's capsule. As technicians operate the machine, the Doctor notices that the system is overloaded and jumps in to avert disaster. Lazarus emerges, looking decades younger. Despite the momentary crisis, his experiment appears to have been a success - but the Doctor is certain there are dangers the professor has overlooked. Lazarus scoffs at the Doctor's warnings, so the Doctor and Martha sneak off to conduct their own tests, taking a DNA sample from Martha's hand, which Lazarus has just kissed. They see that his sonically "hacked" DNA is unstable: Lazarus is changing.

Meanwhile, Lazarus speaks with Lady Thaw. She wants to be the next to be rejuvenated, and to continue their partnership both personally and professionally. He rejects her. As she threatens to complain to Mr. Saxon, Lazarus' financial backer, he transforms into a large, scorpion-like monster with Lazarus' face, and kills her.

Downstairs, Francine asks Tish and Leo whether Martha has ever mentioned the Doctor to them before. She worries there is "something going on". Lazarus returns to the reception, apparently human and wearing a different suit, and invites Tish upstairs with him.

The Doctor and Martha find Lady Thaw's body; the Doctor says she had all the life energy drained to supply energy to the processes caused by Lazarus' fluctuating DNA. Worried he will kill again, they go back downstairs, only to learn that he has gone off with Tish. They rush off, the Doctor accidentally spilling a drink on Francine. Another man replaces her drink, and darkly warns that Martha should be more careful in choosing her friends.

Lazarus takes Tish to the roof, where he talks about nearby Southwark Cathedral and quotes T.S. Eliot, a quote the Doctor completes. As they argue, Martha gets Tish away from Lazarus before he transforms again into a monster. The Doctor comments that what Lazarus has transformed into is an accidentally-unlocked evolutionary dead-end lying dormant in human genes (resembling brontoscorpio, see Walking with Monsters). They run away, tripping a security lockdown. The Doctor gives Martha the sonic screwdriver to unlock the doors, and warns everyone at the reception to get out; but Lazarus kills one woman and Leo suffers a concussion. The Doctor draws Lazarus away from Francine. Lazarus chases the Doctor down a corridor.

Martha examines Leo, gets everyone out of the building, and goes back inside to help the Doctor despite Francine's protests. Tish guesses that "maybe she loves him". The man who replaced Francine's drink earlier calls the Doctor "dangerous", and whispers in Francine's ear the things he says she "should know" about him.

The Doctor turns on the gas in a lab and leaps away from the resulting fireball, but the Lazarus monster survives. Martha returns the sonic screwdriver to the Doctor. They flee together into the capsule of Lazarus' machine, on the Doctor's hunch that Lazarus is unlikely to destroy his own creation. Instead, Lazarus turns it on. The Doctor "reverses the polarity" so that it affects the outside of the capsule instead of the inside, transforming Lazarus back to human in appearance - and killing him.

Outside, as the ambulance carrying Lazarus' body pulls away, Francine slaps the Doctor, and tells him to keep away from Martha. The Doctor hears the ambulance crash and rushes toward it, followed by Martha and Tish. They find two more of Lazarus' victims in it; Lazarus has come back to life. They find him in human form inside Southwark Cathedral, where as a child he took refuge during the London Blitz. The Doctor says he was present during the Blitz, but Lazarus says that he is not old enough to have been there. They argue again about the benefits and curse of longevity. Martha (accompanied by Tish) then lures Lazarus away to the top of the bell tower; the Doctor told her earlier that Lazarus could be defeated if he could just get him up there. As the Lazarus monster chases the Jones sisters at the top of the cathedral, the Doctor pulls out all the stops on the pipe organ, inserts the sonic screwdriver, and plays it at maximum volume, setting up a resonance in the bell above Lazarus that interferes with his sonic-based experiment. Lazarus falls to the cathedral floor below, transforming one last time - back into the elderly man he once was.

Back in Martha's flat, the Doctor offers Martha one more trip, but Martha refuses to go with him on that basis, as a mere passenger being given a treat. The Doctor says "Okay, then, if that's what you want." She thinks he means to leave her again, but he indicates with a nod that she is welcome to rejoin him on her terms, and admits she was "never really just a passenger". They leave together in the TARDIS. As it disappears, Martha's phone rings; it's Francine. She warns Martha about "who this Doctor really is", saying, "This information comes from Harold Saxon himself. You're not safe!"

Cast

 * Tenth Doctor — David Tennant
 * Martha Jones — Freema Agyeman
 * Tish Jones - Gugu Mbatha-Raw
 * Leo Jones - Reggie Yates
 * Francine Jones - Adjoa Andoh
 * Dr Lazarus — Mark Gatiss
 * Lady Thaw - Thelma Barlow
 * Party Guest - Lucy O'Connell
 * Mysterious Man - Bertie Carvel

Crew

 * Organ Performance - David Bednall

Story Notes

 * Gatiss's appearance will make him one of a select few to have both written for and acted in the show, and the first of the new series to do so.
 * The Doctor states that he has to 'reverse the polarity', this was also a common statement used excessively during Jon Pertwee's time as the Third Doctor.

Ratings
The BARB final rating for this episode was 7.19 million viewers.

Myths
to be added

Location Filming
to be added

Discontinuity, Plot Holes, Errors
to be added

Continuity

 * The Doctor saw the Blitz first hand in The Empty Child/The Doctor Dances.
 * The Doctor last wore a suit in Rise of the Cybermen/The Age of Steel.

DVD and Other Releases
This episode will be released alongside Daleks in Manhattan, Evolution of the Daleks and 42.