The Doctor and Sam, looking for a break from saving the universe, land on Kursaal, planet of the theme parks. Unfortunately, as usual, they land five years too early, while the parks are still being built (causing Sam to become quite sulky). The Doctor insists that they go exploring, as usual, and they find an archeological dig... where all but two of the archaeologists have been killed.
The Doctor passes himself and Sam off as a pathologist and nurse intern respectively, and begins to help the investigation into the murders. They soon discover that the history of Kursaal is not quite what it seems, and its ancient species, the Jax, are rising once again.
Tropes present in Kursaal include:
- Amusement Park of Doom: Kursaal, despite its security forces' best efforts.
- Eye Colour Change: Sam's eyes turn green from her usual blue when she's possessed by the Jax.
- Fate Worse than Death: The Doctor says that being taken over by the Jax would be this for Sam.
- Good Thing You Can Heal: As usual, the Doctor gets injured - this time, his fingers are smashed with an axe. He, as usual, heals between books.
- Mind-Control Eyes: Sam's turn from green to blue when she's possessed by the Jax.
- Our Werewolves Are Different: Only the Jax drones behave like ordinary werewolves. The real Jax is a sentient virus that uses the light of the full moon to take full control of its host.
- The Slow Path: Kadjik is very surprised to see that the Doctor and Sam haven't aged in 15 years.
- The Virus: The Jax.
- Weather-Control Machine: How they keep the theme park from being hit by the storms that are normal on Saturnia Regna.