In a Mars base the inhabitants are being infected by a mysterious water creature which takes over its victims. The Doctor is thrust into the middle of this catastrophe knowing a larger one is waiting around the corner.



Watch Now

With Prime Video





Episode cast overview, first billed only:
Aleksandar Mikic ...
Maggie Cain (as Sharon Duncan Brewster)
Lily Bevan ...
Adelaide's father (as Charlie De'Ath)
Rachel Fewell ...
Anouska Strahnz ...


The Doctor arrives on Mars in the year 2059 and joins the first human Earth colony led by Adelaide Brooke. The day he arrives is also the day history records the entire settlement destroyed in an unknown cataclysm with all members of the settlement being killed. Everyone soon realizes that colonists are being infected by some unknown agent and are being transformed into zombie-like creatures. For reasons that are eventually explained, The Doctor is not prepared to save them and tells Brooke that she has to die. He quite torn by this decision and eventually chooses another path, one that will have other repercussions for him in the future. Written by garykmcd

Plot Summary | Add Synopsis


See all certifications »

Parents Guide:





Release Date:

19 December 2009 (USA)  »

Company Credits

Production Co:

Show detailed on  »

Technical Specs


See  »

Did You Know?


This story was initially envisaged as a Christmas special. Several festive references remain, such as the crew on Mars preparing for Christmas dinner, and the snowing when the Doctor arrives back on Earth as he exclaims how he likes snow. See more »


Tarak Ital's name is misspelled as "Tarek Ital" in Yuri Kerenski's obituary. See more »


Adelaide: You saved us?
Adelaide: Just think, though. Your daughter and your daughter's daughter, you can see them again. Family reunion.
Adelaide: [Shakes her head "no"] But I'm supposed to be dead.
The Doctor: Not anymore.
Adelaide: But... Susie... my granddaughter... wasn't she supposed to become... we'll never exist now.
The Doctor: Nah, Captain Adelaide can inspire her face-to-face. Different details, but the story's the same.
Adelaide: You can't know that! And if my family changes... the whole of history could change! The future of the human race! No one should ...
See more »


Featured in Doctor Who Confidential: Is There Life on Mars? (2009) See more »


Doctor Who Theme
Written by Ron Grainer
Arranged by Murray Gold
Performed by BBC National Orchestra of Wales
See more »

Frequently Asked Questions

This FAQ is empty. Add the first question.

User Reviews

Pushing the envelope...
17 February 2015 | by (Argentina) – See all my reviews

I like this episode as one that tries to break new grounds in the established Doctor Who series, getting out of the comfort zone. Here we see the Doctor in another episode flying solo and how this affects his judgment without an opposite like Donna. The companion always challenges some critical decisions of the Doctor. The episode ending shows that and how this might affect his future. It is clear special effects and sets have improved a lot through seasons and this episode has a cinema film feeling in its execution. The enemy here is really scary and not always when visible. Acting is excellent and Mr Tennant shows very well Doctor's conflict at the end. Can't wait to watch next episode.

2 of 5 people found this review helpful.  Was this review helpful to you?

Contribute to This Page

Create a character page for: