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.
The Doctor
Captain Adelaide Brooke
Ed Gold
Maggie Cain
Mia Bennett
Yuri Kerenski
Roman Groom
Steffi Ehrlich
Tarak Ital
Andy Stone
Emily
Mikhail
Adelaide's Father
Young Adelaide
Ulrika Ehrlich
Lisette Ehrlich
Ood Sigma
