The TARDIS materialises inside an Aztec tomb. Outside it, the Doctor and his companions soon discover that Mexico in the 15th century is a bloodthirsty and dangerous place... And with Barbara mistaken for a reincarnation of an ancient high priest called Yetaxa, the history teacher thinks that she can put an end to the barbaric human sacrifices once and for all. But can she rewrite history without disastrous consequences?

In a dystopian future, the Brazilian government decrees a measure that forces black citizens to migrate to Africa in an attempt to return to their origins. Seeing themselves in the center of terror, two cousins take refuge in an apartment, where they debate social and racial issues, and share the same yearning for the change of country.