Voyage of the Damned
This season's fun Christmas romp. The TARDIS crashes into a spaceship called Titanic, but sabotage threatens to bring the ship crashing to Earth, destroying the planet. The "tour director" who gives the tourists to Earth incorrect information about Earth customs is hilarious.
Partners in Crime
The Doctor meets Donna Noble again, both investigating Adipose Industries, makers of a successful diet pill. The pill causes fat to leave the body - in the form of cute little aliens who simply walk away. We're also introduced to Donna's grandfather, the wonderful Bernard Cribbins (who was briefly in "Voyage of the Damned" as a newspaper vendor).
The Fires of Pompeii
Instead of Rome in the first century A.D., the Doctor and Donna land in Pompeii, the day before Mount Vesuvius erupts. The TARDIS is sold to a wealthy merchant as "modern art," the volcano is inhabited by aliens who want to convert the human race to their own kind, and Vesuvius blows. Donna provides - not for the last time - a humanizing influence on the Doctor.
Planet of the Ood
Taking Donna to a random point in time and space, the Doctor encounters an Ood (from "The Impossible Planet"). The Ood are being developed as a slave race.
The Sontaran Stratagem/The Poison Sky
Martha Jones summons the Doctor to help investigate ATMOS, a satellite navigation system that also captures harmful emissions. The developer of the system is a brilliant young man - who turns out to be working for the Sontarans, and together they have devised a plan to poison the Earth's atmosphere so the Sontarans can use Earth to clone more soldiers.
The Doctor's Daughter
A tease of a title, as we discover early on that the "daughter" is a clone. The TARDIS takes the Doctor, Donna, and Martha to a planet in the midst of a multi-generational war between humans and a race of fish-like creatures, fighting over "the Source," a mythological place of power. The episode tries to make a point about war and forgetting what one is fighting for, but ultimately seemed unsatisfying.
The Unicorn and the Wasp
The Doctor and Donna travel to an English country estate in 1926, where they invite themselves to a party, as one of the guests is Agatha Christie. There's a warning about "the Unicorn," a wily jewel thief, and they encounter an enormous wasp creature. One by one, partygoers are found dead, murdered in ways shown in Christie's books. They team up with Christie to solve the case - and, along the way, explain Christie's real-life 10-day disappearance. Nothing deep here, but a fun episode.
Silence in the Library/Forest of the Dead
The TARDIS arrives in a planet-sized library in response to an emergency call, but find no one living. At the same time, a team, including archeologist River Song, arrive to understand the final communication from the Library: "4,022 saved, no survivors." River knows a great deal about the Doctor, including his future, but refuses to provide "spoilers." The group discovers the Vashta Nerada, microscopic creatures that disguise themselves as shadows before devouring their prey. At the same time, we see a young girl in a household with her father, being attended to by a psychiatrist, Dr. Moon. She can see some of the events in the Library. As the group attempts to escape the Vashta Nerada, the two plots ultimately converge. A truly scary episode with a satisfying ending.
While Donna stays at the spa on the resort planet Midnight, the Doctor takes a bus ride to see the Sapphire Waterfall. The Doctor tries to bond with his fellow passengers. The shuttle takes a different route than its usual one, and they run into engine trouble. Soon they hear knocking from outside the bus, from the surface of a planet that is supposed to be uninhabitable. The creature inhabits one of the bus passengers. Frightened, some of the other passengers want to eject the possessed woman, over the objection of the Doctor. Then the creature inhabits him… A taut tale about how humanity behaves in a crisis.
It's a Wonderful Life, Doctor Who-style. On an alien planet, Donna becomes separated from the Doctor. A fortuneteller asks Donna to describe the event that led her to first encounter the Doctor. Donna replies that, in a car trip with her mother, the two argued about which potential job would be better: turn left, and take a temporary job with H. C. Clements (Donna's employer in "The Runaway Bride"), or turn right to apply for a secretarial job (Mrs. Noble's preference). We then see what happens in an alternate history when Donna takes the right turn instead: she never meets the Doctor, who dies in the events of "The Runaway Bride," and is therefore not able to save the Earth again and again. When the Titanic crashes into London (in an alternate version of "Voyage of the Damned"), England declares martial law and descends into a military state. Rose Tyler, working with UNIT, appears to tell Donna that she must go back in time and convince her younger self to make the left turn instead of the right. An interesting concept, though with considerably less meaning to anyone who hasn't watched the episodes referenced in "Turn Left." With the Doctor absent in most of this episode, somewhat less interesting, even if Catherine Tate is better able to carry an episode than some of the other companions.
The Stolen Earth/Journey's End
Before the Doctor and Donna can get back to Earth, the Earth is teleported out of its orbit, joining other missing planets (referenced throughout the past season). The Doctor, following Donna's clue that the bees have been disappearing, tracks the Earth to the Medusa Cascade, a rift between universes. They set out for Earth. Back on Earth, the Daleks subjugate the planet, with pockets of resistance led by Captain Jack Harkness (Torchwood), Martha Jones (UNIT), Sarah Jane Smith, Rose Tyler, and Prime Minister Harriet Jones. They help the Doctor locate the Earth, though the Daleks find and kill Harriet Jones. As the Doctor rejoins Rose, a Dalek shoots and kills him, and he begins to regenerate. He makes it inside the TARDIS, where he is able to halt the regeneration process once he is healed, directing the remaining regeneration energy into his severed hand that has been traveling in the TARDIS since the 10th Doctor's first appearance. Donna touches the hand, which transfers energy to the hand, forming a replica of the Doctor, who saves the TARDIS from destruction by the Daleks. The Daleks' plan is to use the "compression field" from the alignment of the stolen planets to form a "reality bomb" that will destroy all matter in every universe. The although the Doctor and various former companions are captured, the ersatz Doctor and Donna arrive in the TARDIS. A Dalek hits Donna with an energy beam, activating Time Lord knowledge within her (from her touch of the regenerating hand), allowing her to take control of the Dalek machinery, disable the reality bomb, and helping the Doctor destroy the Daleks' ship. The TARDIS tows the Earth back to its correct orbit. The Doctor then returns his companions home, including Rose back to the parallel universe from "Doomsday." The second Doctor is revealed to be part human and unable to regenerate. He stays with Rose. Donna, however, cannot handle the Time Lord knowledge in her head and starts to burn up. To save her, the Doctor removes all memory of their time together and returns her to her mother and grandfather, admonishing them that she can never remember any of it or she will die. He leaves, alone.
A wonderful episode, bringing together a number of plot threads left dangling for a season or more, resolving Donna's time with the Doctor, and reuniting the Doctor (or a Doctor, at any rate) with Rose. As with much of the series, it doesn't pay to think too hard about the logic of the plot, and in an episode like these two it doesn't matter.
Counting the "season" of five episodes as part of series 4, we have:
The Next Doctor
Despite the provocative title, the next Doctor turns out to be a man suffering from amnesia after a Cyberman attack on his family in 1851. The man calls himself the Doctor, holds a pocket watch that could be a Chameleon Arch ("Human Nature," "Utopia"), has a companion and, he claims, a TARDIS - which turns out to be a hot air balloon. The Cybermen are working with Mercy Hartigan, a woman bitter that her gender holds her back from dominating society. She uses children from workhouses and orphanages to work on behalf of the Cybermen. They ultimately betray Hartigan, converting her to the controller for the "Cyber-King," a enormous mechanical device that wreaks havoc on London. The Doctor uses the hot air balloon to get near the monster, severing Hartigan's connection to the Cyber-King, which topples over. Both Jackson, the false Doctor, and Hartigan regain control over their lives because of their emotions, something the Cybermen lack, suggesting that human emotions are ultimately an asset to the race. A fun story, if a slight one.
Planet of the Dead
In present-day London, Christina, a young thief makes a daring break-in to a museum to steal a golden chalice, escaping on a London bus. On the bus, the Doctor is tracking a wormhole. As the police close in, the bus goes through the wormhole to a desert planet. They need to repair the bus before return to Earth through the wormhole. As a desert storm approaches, the Doctor and Christina explore the surrounding area, discovering a species called the Tritovores, whose ship has crashed on the planet. The Tritovores explain that this was a thriving world, with billions of inhabitants and was not desert-like. They send out a probe that discovers the "storm" is really a swarm of metallic, stingray-like aliens that devour everything living on a planet before creating a wormhole to their next destination - in this case, Earth. The Doctor, with Christina's help, fixes the bus in time to move it through the wormhole, where UNIT is waiting to close the wormhole before the aliens can travel through it. Interesting story, and terrific interaction between the Doctor and Christina, who gives as good as she gets.
The Waters of Mars
The Doctor travels to Mars in 2059, where he finds the first human base on Mars - Bowie Base One - and is taken captive, and led to the base commander, Captain Adelaide Brooke. The Doctor realizes that the date is the day on which the base is destroyed, with no survivors, though Brooke's descendants would eventually head to space and begin to explore the universe. He notes that the event is fixed in time, and thus he can't change it. Before he can leave, the crew begins to develop problems in the bio-dome - the water appears infected by a water-based life form. Though Brooke, her crew, and the Doctor try to contain the infection, they are unable to do so. Rather than risk bringing the life form back to Earth, Brooke recognizes she has no choice but to destroy the base. The Doctor, however, decides that, as the last Time Lord, he answers to no one, and uses the TARDIS to save the remaining uninfected crew members, including Captain Brooke. Back on Earth, Brooke says to him that no one should have that much power. She enters her house and kills herself in order to try to maintain the time line. The Doctor realizes he has gone too far.
I liked the episode on its own - it was a scary little tale with a race against time to discover the cause of the infection and then devise a way to defeat it before all the crew died - and the ending, with its tie-in to the next two episodes, gave it additional emotional impact.
The End of Time, Parts 1 and 2
The Doctor learns from the Ood that the Master will return, heralding the end of time, and that the Doctor's life will end soon. Acolytes of the Master attempt to bring him back from the dead. His human wife, Lucy Saxon, partially thwarts the effort, leaving the Master in a state of constant energy expenditure, which allows him superhuman strength and the ability to throw off that energy, but also constantly hungry. The Doctor finds Wilfred Mott, Donna's grandfather, and tracks the Master. The Master, however, is kidnapped by billionaire Joshua Naismith, who believes the Master can fix a device that will make his daughter immortal. Though the Doctor and Wilf track the Master to the Naismith mansion, they are too late, as the Master has fixed the device to place his own DNA into everyone on Earth, save for the Doctor, Wilf, and Donna. The Time Lords are shown, planning a way out of the time lock that the Doctor has placed them in just before Gallifrey is destroyed. The Time Lords lock on to the sound in the Master's head by means of a white star, and bring Gallifrey to Earth. The Doctor destroys the white star, breaking the link and sending Gallifrey back to its fate. When the Lord President attempts to kill the Doctor, the Master, enraged that the Time Lords betrayed him, intervenes and is himself killed. Alone with Wilf in the Naismith mansion control room, the Doctor hears four knocks, the sound that was foretold would signal his death. Wilf has locked himself into a chamber that will soon be flooded with radiation. Though the Doctor first wails that it's unfair and that he doesn't want to die, ultimately he takes Wilf's place in the chamber. The radiation floods his body and the regeneration process begins. He has enough time left in his current body to visit his past companions - sometimes saving them, sometimes just interacting with them - before he regenerates into the Eleventh Doctor.
If the coda - the Doctor's "reward" - doesn't bring tears to your eyes, you might have the emotional center of a Cyberman.