Episode title: The Waters of Mars
Featuring: Tenth Doctor
Companions: Adelaide Brooke
First shown: 15th November 2009
Guide: The episode starts with the Doctor wandering around Mars in his spacesuit when he is detained by a human colony, Bowie Base One. Bowie Base One is under the command of Captain Adelaide Brooke, whose death is to occur on that day along with the rest of the Bowie Base One crew. The Doctor is unwilling to interfere, as these deaths and the explosion that destroys Bowie Base One is a fixed event in time, and decides that he has to leave Mars. Before he can do such an act, a crisis develops within the base. Two colonists, Andy Stone and Maggie Cain have been infected by a life form that is causing them to gush large amounts of water from their bodies. The virus spreads quickly, with Andy passing it onto Tarak Ital.

The change in appearance to the crew after the infection is within their body.

Maggie is contained within the Medical Wing, and the organism that is in her body reveals its intention to reach Earth, a planet that is rich in water. The crew decide that it is too dangerous to remain on the base and begin to evacuate in the escape shuttle. Before the Doctor also makes his departure, he tells Adelaide that she must die on the base on Mars on that day for history to continue as it should. As the Doctor begins to return to his TARDIS, Andy and Tarak mount an external attack on the base’s outer shell, exuding water that cascades into the base’s control room, infecting both Steffi Ehrlich and Roman Groom. Maggie also breaks out of the Medical Wing and infects Ed Gold, who manages to trigger the escape shuttle’s self-destruct mechanism before the infection takes hold of him. This kills him but leaves the infection stranded on Mars, though the remaining surviving crew have no means of escape. The Doctor witnesses the explosion and is overcome with defiance against time itself and turns back to try and save the others. He tries various methods of fighting the water but they are undone quickly. Adelaide activates the base’s self-destruct sequence to destroy Bowie Base One and leave the virus trapped on Mars with no more crew for it to infect. As one last resort, the Doctor uses Roman’s robot, GADGET to access the TARDIS and fly it into the control centre to rescue Adelaide, Yuri Kerenski and Mia Bennett before the base is destroyed.

Adelaide in Bowie Base One with the Doctor and Maggie.

The TARDIS takes everyone back to Earth, outside Adelaide’s house. Yuri and Mia are shocked by what has happened and depart, leaving Adelaide alone with the Doctor. He gives his reasoning for meddling with the events that he should have left alone, saying that he is the last Time Lord and has total authority over time. He pronounces himself the “Time Lord Victorious.” But Adelaide scolds the Doctor for his new found arrogance and says that “the Time Lord Victorious is wrong.” Adelaide returns to her house and commits suicide, thus rendering events the same with minor changes, that she died on Earth instead of Mars, and Yuri and Mia tell Earth what happened to Bowie Base One. The Doctor is overcome with emotion at what he’s done, and realises too late that his hubris will have consequences. Ood Sigma appears in the street with the Doctor. The Doctor asks if it is time for him to die, to which Ood Sigma is unresponsive, and disappears. The Doctor staggers back to the TARDIS and the ominous sound of the Cloister Bell rings out.

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