The Tardis materializes in Twelfth Century Jerusalem, during the Third Crusade, and the time-travellers emerge in the middle of a Saracen ambush. Barbara is captured, but the rest of the crew stop the attackers from killing William de Tornebu, a friend of King Richard.
Barbara is presented to Saphadin (Roger Avon) the brother of Saladin (Bernard Kay). The Saracens believe she is Lady Johanna, sister of King Richard. Ian asks to be allowed to rescue her, so he is knighted as Sir Ian of Jaffa and is sent as an emissary to Saladin’s court to ask for her release and to offer Saphadin the hand of the real Lady Johanna (played by Jean Marsh), though she refuses to sacrifice herself for peace.
While Ian is searching for Barbara, he is attacked by the bandit Ibrahim (Tutte Lemkow) and tied to stakes in the hot sun. He tricks and overpowers Ibrahim, then convinces him to help in the search for Barbara, who has escaped custody and is hiding in a harem. The Doctor attempts to escape to the TARDIS, is caught by the Earl of Leicester (John Bay) who thinks he is a spy for Saladin and sentences him to death. “Sir Ian” arrives to carry out the execution, but everyone escapes in the TARDIS.
The story was praised by critics, but two of the four episodes were erased and never recovered. Though the Saracen characters were portrayed with sympathy and respect, the story was not released in the Middle East.