The Tenth Doctor and Donna arrive in the Andromeda Galaxy and are caught in a race across space with the Cult of the Shining Darkness.
- Ancient Astronauts: Parodied with the Jaftee of Karris, who collect religions.
- Briar Patching: The Doctor tells Ogmunee he doesn't want the sphere but he takes it. It turns out to be a bomb, which destroys the Dark Light and the last of the Cult.
- Continuity Nod: The Doctor mentions the Isop Galaxy.
- The previous book "The Doctor Trap" is mentioned when Donna talks about robots.
- Fantastic Racism: The Cult of Shining Darkness want to kill robots not under their control.
- Humanoid Aliens: The Dallendafs and other Andromedans.
- Plot Coupon: The four components to build a device to free the Torch from Sentilli.
- What Measure Is a Non-Human?: Overlaps with...
- What Measure Is a Non-Cute?: Donna is upset when a robot resembling a woman is damaged but dismissive when a more sentient and robotic-looking robot is damaged. This is lampshaded.
