Kursaal is a pleasure world, a huge theme park for the Cronus system - or rather it will be if it isn't destroyed during construction.

Eco-terrorists want the project halted to preserve vital archeological sites - areas containing the last remains of the long-dead Jax, an ancient wolf-like race, whose remains are being buried beneath the big-business tourist attraction.

Sam falls in with the environmentalists and finds her loyalties divided.  Meanwhile, the Doctor's own investigations lead him to believe the Jax are not extinct at all.

Cut off from the TARDIS, separated from his companion and pursued for murder, the Doctor realises Kursaal hides a terrible secret - and that Sam is being affected by events more than anyone would guess...