Marcus Didius Alexander Postumus is a special boy. He is twelve, or perhaps eleven. He has two mothers and various possible fathers, so he worries who will take care of him. He is self-confident yet vulnerable, intelligent yet sinister. He knows not many people like him.

When his birth mother, Thalia the snake-dancer, takes him to live with her troupe of exotic performers, Postumus sees it as useful experience even though it involves him mucking out menagerie cages. No one anticipates how much havoc he will wreak.

On his first day a tragedy occurs. No one else cares, so Postumus decides he alone must solve this crime and impose retribution on the guilty. As son and brother to the famous investigators Falco and Albia, he knows murder is punished by execution. Postumus single-mindedly sets out to accomplish this, sidetracked by nothing, not even a rehearsal of Falco's legendary play, The Spook Who Spoke...