The Hills of Varna - The Crown of Violet

In 1952 Trease wrote a prequel to The Hills of Varna, The Crown of Violet. The title is taken from a quote from Pindar (see City of the Violet Crown). Set in ancient Athens, it is about how Alexis wrote The Gadfly, a comedy defending Socrates, and contains vivid descriptions of the Greek theatre. As in The Hills of Varna and Cue for Treason, the hero befriends a spirited, convention-defying girl who plays a vital role in the adventure.

Its American title Web of Traitors refers to the subplot of a planned coup d'état against the Athenian democracy; a speech in Alexis's play is used to trick the plotters into revealing themselves.

This could be a record, outside of science fiction and fantasy, for how far the events of a prequel have preceded the first novel.