'I might have know it,' the Brigadier said tersely. 'The Doctor and Miss Shaw have managed to lose themselves on an island that doesn't exist.'

1934: Salutua, a legendary lost island in the Pacific. Millionaire Marshal J Grover's expedition arrives to uncover and exploit its secrets. But the task is complicated by a film star's fears and ambitions and a scientist's lethal obsession.

Nearly forty years later: UNIT headquarters, London. The Doctor and Liz Shaw are asked to identify a mysterious artifact and trace its origin. The trail leads them back in time to Salutua and a gigantic discovery. Meanwhile, the Brigadier faces and epidemic of UFO sightings and supernatural occurrences that threaten to bring about global panic. Only the Doctor can help him - but he's trapped on a mythical island four decades in the past.