A strange signal from Earth draws the TARDIS to the island of Lanzarote, where Turlough rescues a young American girl, Peri, from drowning. Among her possessions is an artefact bearing an alien symbol - the same triangular mark that Turlough has branded into his arm. The mystery deepens when Kamelion falls under the control of a powerful mind, and the TARDIS travels to the volcanic world of Sarn. As Turlough is forced to face his past, the Fifth Doctor must stop his oldest enemy from harnessing the revitalising powers of Numismaton gas...
Peter Davison
as The Doctor
Mark Strickson
as Turlough
Nicola Bryant
as Peri Brown
Anthony Ainley
as The Master
Peter Wyngarde
as Timanov
James Bate
as Amyand
Dallas Adams
as Professor Howard Foster
Jonathan Caplan
as Roskal
Edward Highmore
as Malkon
Barbara Shelley
as Sorasta
Michael Bangerter
as Curt
Richard Simons
as Father
