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.
| Writing | Russell T Davies | Writer |
| Writing | Phil Ford | Writer |
| Directing | Graeme Harper | Director |
| Production | Russell T Davies | Executive Producer |
| Production | Julie Gardner | Executive Producer |
| Production | Debbi Slater | Associate Producer |
| Production | Nikki Wilson | Producer |
| Camera | Ernest Vincze | Director of Photography |
| Editing | William Oswald | Editor |
| Sound | Murray Gold | Music |
