Aired Jan 3 - Jan 24, 1976
Written by: Robin Bland
Directed by: Christopher Barry
The Doctor and Sarah arrive on Karn, a desolate planet that seems to be a magnet for crashed spaceships. Karn is also home to a mysterious Sisterhood, a group of women who guard a sacred flame that produces an elixir of life. Also on Karn is renegade scientist Mehendri Solon, who is there performing secret experiments in an attempt to construct a new body for the living brain of Morbius, a Time Lord criminal believed to have been executed.
Upon meeting the Doctor, Solon is convinced that his head is the perfect receptacle for Morbius' brain, and begins making plans to obtain the Doctor's head and transplant it onto the body Solon has cobbled together from spaceship crash victims. The Sisterhood meanwhile, believing that the Doctor has been sent to Karn by the Time Lords in an attempt to steal the final drops of elixir produced by the dying flame, attempt to burn the Doctor at the stake. Though he's rescued by Sarah, she is temporarily blinded while doing so.
The Doctor drinks Sarah to Solon to see if the scientist can help her, but Solon tricks the Doctor into believing her condition is irreversible. In desperation, the Doctor returns to the Sisterhood in the hopes that the elixir will help, but the Sisters cannot spare any as the flame is dying. Meanwhile, as Sarah's sight slowly returns, she uncovers Solon's plan to create a monstrous new body for Morbius and unleash his evil across the universe once more.
The Doctor successfully restores the flame, which will now begin producing elixir in earnest, and returns to Solon's laboratory, but only succeeds in being captured in the cellar alongside Sarah. Solon has by this point begun the procedure to transplant Morbius' brain into a synthetic brain case and attach it to the body he has constructed. The Doctor manages to use the chemicals at hand in the cellar to create cyanide gas, and wafts it into the ventilation system. While Solon is killed, the now ambulatory Morbius survives.
Morbius then challenges the Doctor to a Gallifreyan psychic battle, and though the Doctor proves victorious, the contest extols a heavy cost to both. The insane Morbius wanders onto the planet's surface, where the Sisters drive him off a cliff to his death. The injured Doctor is revived by the elixir of Karn, and he and Sarah leave with the gratitude of the Sisterhood.