The philosopher/mathematician/mystic Pythagoras shares a prison cell with the layabout Coriander, but seems maddeningly indifferent to such mundane details as their impending executions. Coriander is infatuated with the local heart throb Lyra, whose day job is, unfortunately, Poisoner's Assistant. They both want Pythagoras's secret knowledge—he in order to escape, she to become a Muse. But Pythagoras won't let them distract him from wrestling with the birth of an idea, something about a hypotenuse.