Doctor Who (William Hartnell) and the crew of the Tardis find themselves inside of a 15th-century Aztec temple. Things soon go awry when Barbara is worshiped by the civilization as the goddess Yetaxa. Barbara decides to take advantage of her newfound status as a deity and decree that her subjects cease their ancient practice of human sacrifice. The Doctor is wary of the dangers of altering human history, however, and aims to stop Barbara and get his crew out before it's too late.