The Doctor visits Tenochtitlan to see an old friend, a merchant named Tochtli, who is really a spy for the Aztec empire. Tochtli is wary of the Doctor, wondering if he will have to kill him. As they walk through the market, they are accosted by several young warriors, but the Doctor stares them down.
At Tochtli's home, he and the Doctor discuss the "bonepuppets", aliens who tried to wipe out Earth thirty years ago but were stopped by Tochtli's parents. Tochtli's mother, Xoco, had the ability to extract knowledge from objects, and learned of the bonepuppets' plans through a piece of their garbage. With this knowledge, the Doctor was able to defeat their plans.
Now, the Doctor wants Tochtli to perform the same service for him. Tochtli, angry that the Doctor knows about his psychic ability, of which not even his wives are aware, tries but fails to kill the Doctor. He takes a look at a bonepuppet seed, which itself is harmless, but by touching it Tochtli can read the bonepuppets' intentions, which are to destroy another planet. With this knowledge, the Doctor will be able to stop them.
Before he leaves, he tells Tochtli that he is braver than the warriors, because he risks his life for little credit or glory.
to be added
to be added