New Earth was the first episode of series two of the revived Doctor Who, and the middle of a loose “New Earth” trilogy incorporating The End of the World and Gridlock. It featured reappearances of Cassandra O’Brien.Δ17 and the Face of Boe, both last seen in End of the World, and introduced a mystery surrounding the Face that would later be a major part of the overall story arc of series three. It was also the first BBC Wales episode to be set on an alien world (with the exception of a brief beginning scene of Rose saying her goodbyes on Earth), the entirety of series one having taken place on or in orbit of Earth.
Behind the scenes, it was the final appearance of Zoë Wanamaker, but it was the first time that actors Anna Hope and Adjoa Andoh worked on the program. Principal photography was rocky enough to be remarked upon by two different sets of commentators. Its overruns and difficulties negatively impacted upon other episodes within its production block.
Series two also played host to a series of mini-episode prologues for each new episode, known collectively as Tardisodes. Tardisode 1, the first of these short preludes, led into New Earth.
The Tenth Doctor powers up the TARDIS as Rose says good-bye to Jackie and Mickey at the Powell Estate. Although Jackie and Mickey sadly watch the TARDIS fade away, inside the ship Rose is all smiles as she asks where they are going next. The Doctor tells her that they are going further than they have ever gone before.
The TARDIS materializes on New Earth, in the year five billion and twenty-three. Following the destruction of Earth, humanity became nostalgic and settled a new planet with similar gravity and atmosphere in Galaxy M87. Rose is delighted at the new world, the sight of the futuristic city of New New York in front of them and the smell of apple-grass. However, the two travelers are being observed by a metal spider controlled by Chip, a small, pale man with multiple tattoos. Chip takes his orders from Lady Cassandra, who is still alive and recognizes Rose.
The Doctor and Rose head for New New York Hospital, a hospital to which the Doctor has been summoned by a telepathic message displayed on his psychic paper: “Ward 26, Please Come”. The hospital is run by humanoid feline nuns belonging to an order called the Sisters of Plenitude. Trying to find the right ward, the Doctor and Rose enter separate lifts, which drench each of them in a disinfectant liquid then blow-dry them — the Doctor is completely blasé about it, while Rose has no idea and takes a while to get used to it. Chip has overridden Rose’s lift controls, diverting her to the basement. He beckons her forward, calling her by name; she grabs a metal pipe as a weapon.
In the ward, the Doctor is escorted by Sister Jatt. He sees that the patients all have diseases which are supposed to be incurable, yet the Sisters are able to cure them. The nuns are evasive about what is in the colored solutions that are given to the patients. The Doctor recognizes who has called him here — the Face of Boe. He is being tended by Novice Hame, who tells the Doctor that the Face is dying of old age — the one thing the Sisters can’t cure.
Rose explores the basement warily, and finds a film of a party of several men and a blond woman with a familiar voice. The same voice makes Rose turn to see Cassandra: a piece of skin stretched out on a frame over a brain jar. Cassandra had been reconstructed from another piece of her skin, and Chip — a force-grown clone devoted to Cassandra — smuggled her into the hospital, where he has been tending to her ever since. Cassandra has found out the Sisters are hiding something, and she needs Rose’s help… or rather, her body.
Using a device called a psychograft, Cassandra transfers her consciousness into Rose’s mind, taking control of her body but allowing her old one to die. Cassandra is initially unimpressed with her new body — protesting, “I’m a chav!” — but changes her mind after taking a good look at Rose’s curves.
In the ward, Novice Hame tells the Doctor that legend says the Face has lived for thousands, perhaps millions of years and that he will give his dying message to a wanderer without a home. The Doctor realizes that he fits the description in the legend, but says nothing. Below, Cassandra reads Rose’s surface thoughts and discovers that the man with Rose is the Doctor with a new face. She goes to meet him after putting a tiny bottle in her cleavage.
Cassandra’s odd behavior in Rose’s body — at one point giving the Doctor a lusty kiss — raises the Time Lord’s suspicions. They enter Intensive Care and discover the horrifying secret of the cures: hundreds of pods, each holding an artificially grown human being infected with a thousand different diseases, a human farm to breed cures. The Sisters kill any healthy enough to speak or move. The Doctor confronts Novice Hame, but she insists that these artificial humans are just “flesh”, and that it was necessary to cope with the influx of patients and diseases. He demands they reverse what they have done to Rose, not realizing that it is Cassandra who has taken over. Her cover blown, Cassandra reveals her identity and knocks out the Doctor with some drugged perfume.
While the Doctor is trapped in a pod about to be injected with diseases, Cassandra tries to blackmail Matron Casp, demanding money to keep quiet about the Sisters’ actions. Casp declines and threatens her physically. Cassandra releases some of the plague carriers in response. They, in turn, release the rest, and the zombie-like mass of them lurch through the hospital, infecting and killing anyone they touch almost instantly. After failing to find a way out through the basement, the Doctor demands Cassandra release Rose, threatening her with the sonic screwdriver.
Cassandra transfers her consciousness to the Doctor instead. Rose climbs up the lift shaft with a now Cassandra-controlled Doctor, pursued by the carriers. Matron Casp tries to stop them, but is infected and falls screaming down the shaft. Cassandra transfers herself to a plague carrier so that the Doctor can use the sonic screwdriver to unseal the lift doors, then jumps back into Rose. Cassandra is shocked by the loneliness of the carriers, having read the surface thoughts of the carrier she had possessed — not being able to touch or be touched all their lives.
The Doctor and Cassandra reach Ward 26, which seems to be the only place still untouched by the carriers. He grabs all of the intravenous solutions, straps them to his body, then slides down the shaft to the lift car with Cassandra, where he empties the solutions into the disinfectant reservoir. He opens the doors, luring several plague carriers inward as Cassandra starts the shower. The spray drenches the carriers, curing them, and the Doctor encourages them to pass it on; they wander back out to spread the cure to the others. A new race is born: the new humans.
The surviving Sisters are arrested by the New New York Police Department, and the cured new humans are taken into care. The Doctor remembers the Face of Boe, and runs to him. No longer dying, the Face tells him telepathically that he had grown tired of the universe, but the Doctor has taught him to look at it anew. The Doctor asks the Face about his message, but is told it can wait for their third and final meeting. The Face teleports himself away.
The Doctor orders Cassandra to leave Rose’s body at once, telling her to end it. In response, Cassandra sobs and tells the Doctor she doesn’t want to die. Chip then appears — “a volunteer”. Despite multiple protests from the Doctor, Cassandra transfers her consciousness into him. Unfortunately, his “half-life” body quickly fails, and Cassandra accepts her impending true death; New Earth has no place for people like her and Chip.
The Doctor does one last favor for Cassandra, taking her back to the party seen earlier, to the last time anyone had called her beautiful, to re-witness her life as it was in its prime. “Chip” approaches the Cassandra of the past and sincerely remarks on her beauty, before collapsing into the younger Cassandra’s arms as she comforts “him”. As Cassandra finally dies, the Doctor and Rose silently leave in the TARDIS, letting things end, and life take its natural course.