The Doctor uses the TARDIS to take Rose to the farthest point he's ever taken her, to the year five billion and twenty-three in the M87 galaxy. Humanity, after the destruction of the Earth, settled onto a very Earth-like world, called "New Earth", and Rose admires its beauty. The Doctor is summoned to "Ward 26" in a hospital in New New York through his psychic paper, and while he travels to the Ward, gets separated from Rose. In the Ward, the Doctor meets several humanoid feline nuns of the Sisters of Plenitude who are overseeing the patients, all who have incurable maladies but are somehow being cured by the Sisters. The Doctor recognizes the Face of Boe, who reached out to the "the Lonely God" in order to give him a message before he died of old age.
Meanwhile, Rose is brought to the basement of the hospital, where she is escorted by Chip to meet Lady Cassandra, who has survived from her previous encounter with the Doctor and has been watching the two since they arrived. Chip has been using the hospital facility to care for Cassandra, but Cassandra is suspicious of the methods used in the hospital and requires Rose's help. Rose is taken in by this, allowing Cassandra to use a "psychograft" that allows her to implant her mind into Rose's, leaving her old "body" to die. Cassandra can read Rose's thoughts, and knowing of the Doctor's new form, goes to meet him as "Rose". The Doctor is suspicious of "Rose"'s actions, such as kissing him passionately or having knowledge of the advanced computer systems, but is more concerned on how the hospital can cure the incurable. He and "Rose" discover that the hospital houses hundreds of pods containing artificially-grown humans, forcibly inflicted with numerous diseases, such that the Sisters can discover their cures. The Doctor accuses the Sisters of the atrocity, though they insist it was necessary to deal with the influx of patients. The Doctor, believing that Rose's current actions are also a result of being a test subject, is suddenly knocked out by "Rose" using a perfume gas, and locks him in one of the pods. "Rose" then approaches the lead Sister, Matron Casp, demanding payment for her to keep quiet about the hospital secrets, and when she is refused and threatened physically, releases the Doctor and some of the humans as a distraction, but the infected humans further release the others, and a zombie-like attack begins, with those infected trying to attack anyone healthy.
The hospital is put into quarantined as the Doctor, "Rose", and the remaining Sisters try to flee the lower levels. To help their escape, Cassandra is able to jump her mind between other bodies, including one of the infected humans, before jumping back to Rose, and learns that those humans feel a strong sense of loneliness of not being able to touch or be touched. Eventually, the Doctor and "Rose" reach Ward 26, and grab all the intravenous medical solutions; emptying them into a disinfectant shower, they are able to spray the mixture onto a group of the infected humans, who within moments become cured of their diseases. The Doctor encourages them to go and spread the cure to the other infected people, and soon, the attack is over. The police arrest the surviving Sisters, while the Face of Boe, who has also been cured, tells the Doctor that the message for him can wait until their third and final meeting, and then teleports away.
The Doctor now orders Cassandra out of Rose's body. Cassandra transfers her consciousness to a willing Chip instead, but his cloned body begins to fail, and Cassandra accepts her impending, true death; the New Earth has no place for people like her and Chip. The Doctor does one last thing for Cassandra, taking her back to see herself on the last night someone had called her beautiful. "Chip" approaches the Cassandra of the past and tells her just that, and collapses into the younger Cassandra's arms as she comforts "him". As the older Cassandra finally dies, the Doctor and Rose silently leave in the TARDIS.
Doctor David Tennant (Tenth Doctor)
Companion Billie Piper (Rose Tyler)
Camille Coduri – Jackie Tyler
Noel Clarke – Mickey Smith
Zoë Wanamaker – Cassandra
Sean Gallagher – Chip
Doña Croll – Matron Casp
Michael Fitzgerald – Duke of Manhattan
Lucy Robinson – Frau Clovis
Adjoa Andoh – Sister Jatt
Anna Hope – Novice Hame
Simon Ludders – Patient
Struan Rodger – Face of Boe
Writer Russell T. Davies
Director James Hawes
Script editor Simon Winstone
Producer Phil Collinson
Executive producer(s) Russell T. Davies
Production code 2.1
Series Series 2
Length 45 minutes
Originally broadcast 15 April 2006