WhileDoctor Whois known for its bright, optimistic, and often quirky tone, many of its most iconic stories are the ones that abandon this lighthearted feel for something much darker — like the famous “Blink” that first introduced the Weeping Angels, to the downright chilling “Midnight”. But one specific episode stands out as the darkest one of all, and it’s arguably one of the single greatest episodes in the entire series.
The episode in question is none other than the 2009 episode “The Waters of Mars”, starringDavid Tennant ofJessica JonesandGood Omensfame as the Tenth Doctor. The story takes place following the events of the Season 4 finale “Journey’s End”, in which the Doctor parts ways with his traveling companion Donna Noble (Catherine Tate), leaving him to travel space and time completely alone for the first time in the revived series. Right away, the fact that the Doctor has no companion gives this episode an uncanny, melancholy feel — it’s an uncomfortable disruption of the series formula, and one that definitely doesn’t bode well for the Doctor.
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The episode’s setup is a simple one — the Doctor arrives on Marsfor a nice relaxing visit,with no intentions of getting entangled in yet another world-saving misadventure. However, he quickly stumbles upon a human base and is confronted by the crew, who are obviously shocked to see an intruder. The Doctor is confused at first, but soon realizes that he’s in Bowie Base One, the first human colony on Mars. But to make matters much more complicated, he’s arrived on November 21st 2059, the day that the crew of Bowie Base One is destined to die in a mysterious explosion.
While the Doctor is normally quick to save innocent people from danger, even if it means meddling in history to do it, something about this time is different. The Doctor’s cheerful attitudeturns into dread and sorrowas he apologizes to the crew, saying that he needs to leave immediately. But of course, it isn’t that easy. The base is soon infiltrated by a sentient virus known as the Flood, which possesses living beings by inhabiting water. The crew of Bowie Base One becomes infected by the Flood one by one, transforming them into decaying, zombie-like creatures with water seeping from the cracks in their flesh. While the Flood haven’t become as iconic as other horror-themed monsters like the Weeping Angels or Vashta Nerada, their unsettling appearance and threatening nature make them the perfect antagonist for this episode.
As they hide from the Flood,the crew’s leader Captain Adelaide Brooke (Lindsay Duncan) tells the Doctor why she was so determined to go to space in the first place. As a child, she witnessed the Dalek invasion of Earth during the events of “Journey’s End”, but the Daleks spared her for some unknown reason. Adelaide’s encounter with alien life inspired her to journey into the stars herself. Then, the Doctor reveals why the Daleks spared her, and why he’s forbidden from interfering with the Flood’s attack — Adelaide’s death is a fixed point in time that will change the course of history by inspiring her descendants to lead humanity across the entire galaxy. But whilethe knowledge of her legacycomforts Adelaide, she still condemns the Doctor’s refusal to help.
As the Flood continues to thin the crew’s numbers, the Doctor manages to escape Bowie Base One. But as he walks away from the burning base, his guilt becomes too much to bear. After all, this is the Doctor: he simply can’t stand by and do nothing while people are suffering. And as he remembers the code upheld by the Time Lords to never change history, the Doctor comes to a realization. The Time Lords are all dead — all except for him. And so, there’s no one left who can stop him from saving Adelaide and her crew. In the battle between the Doctor’s compassion for those in need and hisresponsibility to protect the timeline,his compassion wins out.
The Doctor returns to Bowie Base One to rescue the last remaining crew members: Adelaide, Yuri, and Mia (played by Eternals star Gemma Chan). At first, the crew are overjoyed that the Doctor’s come back for them. However, Adelaide quickly sees that the Doctor’s compassion has given way to unhinged desperation. The Doctor’s famous line in this scene — “The laws of time are mine, and they will obey me!” — calls to mind the catchphrase of his longtime nemesis the Master, “You will obey me.” Despite his good intentions, it’s clear that theDoctor’s power is going to his head.
The Doctor takes the crew back to Earth in the TARDIS, but Adelaide is starting to have second thoughts about his choice. He insists that Adelaide will still inspire her descendants despite her survival, and that the future will remain unchanged. But Adelaide isn’t convinced, stating that no one should have the power to rewrite history as they see fit. The Doctor stubbornly dismisses her protests, declaring himself “the Time Lord Victorious” as he takes pride in the fact that he’s finally managed to save someone besides “the little people.” After all the losses he’s endured, the Doctor has become drunk on hisnewfound sense of control,reveling in the power to finally decide who lives and who dies.
However, Adelaide refuses to let one man dictate the course of history or place value on one life over another. And so, after stepping back inside her house, Adelaide takes her life with her own laser pistol to ensure that her death will remain a fixed point in time, leaving history unchanged. The Doctor is horrified, immediately realizing that his own actions were the cause of this tragedy. “I’ve gone too far,” he tells himself as he falls to his knees in anguish. This is the moment that marks “The Waters of Mars” asthe single darkest episodein all ofDoctor Who— and quite possibly its best.
The episode is one of the best character studies in the series’ history, pushing the Doctor to his breaking point until he finally snaps under the pressure of his own helplessness. The Doctor’s compassion has always been his greatest strength, driving him to selflessly save everyone he can. But this time, that need to save everyone is twisted into a prideful god complex. Broken by his own sense of powerlessness, the Doctor tries to seize control of time itself, only for his hubris to backfire immediately. Though it’s never stated explicitly, this episode shows why the Doctoralways needs a companion— without a human confidant to keep him grounded, he risks losing his own humanity.
“The Waters of Mars” is one of the highlights of David Tennant’s run. It expertly blends horror and tragedy while also showcasing exactly why the Doctor is such a nuanced, compelling protagonist. And of course, it features David Tennant providing one of his best performances in the entire series. It may be one of the darkest episodes inDoctor Whohistory, but it’s a major contender for one of the best-written stories in the show’s history.
