Peter Davison (The Doctor), Janet Fielding (Tegan Jovanka), Sarah Sutton (Nyssa), Honor Blackman (Anahita), Adrian Lukis (Byzan), David Warner (Siris), Vernon Dobtcheff (Shamur), Matt Addis (Albis), Emerald O'Hanrahan (Mira), John Banks (Radulf Varidi)
During one of Nyssa's experiments, the TARDIS's temporal scanner picks up a message: 'Idra'. Just one word, but enough to draw the Doctor to the Archipelago of Sirius.
There, the Autarch is about to announce a new crusade. A mighty war against Seth, Prince of the Dark...
But who is Seth? What is the secret of Queen Anahita, Mistress of the Poisons? And what terror awaits on Level 14?
(Duration: 120' approx)