sect; a giant, predatory Allosaurus, displaced from the distant past, rampages in the countryside...) Calvus, though taken for a male, is actually a female (of sorts) sent back from the far distant future to destroy the seed creche or "brood chamber" of monstrous aliens—intelligent social insects—who, by her time, have multiplied into billions, emerged from their underground creches, and are in the process of destroying the human race. As a desperate measure a set of six mutually telepathic sisters, including Calvus, are specially bred to be sent on the mission together. (The book hints that the future human race has evolved to be somewhat different from ourselves, and that the six sterile sisters—akin to worker ants or bees—are uncommon only in their preparation for this particular mission; there is a suggestion that, waging an existential struggle against social insects, future humanity was driven to emulate these enemies...) Calvus is the only one of the siblings to arrive at the proper time in the past; there are strong hints that the presence of a handful of extinct creatures such as dinosaurs and sabre-toothed cats in Aulus' time are a side effect of the unintentional displacement of the other siblings into the far distant past. The time-travel technology did not allow Calvus to take any weapons or other gadgets along, so she herself serves as the weapon. She has a limited ability to influence the thoughts of humans other than her sisters—which is how she induced the emperor to issue orders for the Bureau's cooperation—and at the end of the story she destroys the creche by self-destructing as a nuclear or thermal bomb. Before then, through her association with Aulus and separation from her sisters, she learns to experience her humanity almost in the way ordinary humans do. Characters Aulus Perennius: a middle-aged Roman spy, ace agent of the Bureau of Imperial Affairs Gaius: a young cavalry officer, Perennius' protégé, and of whom a startling revelation is made at the book's very end Marcus Optatious Navigatus: Director of the Bureau of Imperial Affairs, like his agent totally dedicated to the crumbling Empire Calvus: the mysterious man who initiates the perilous mission, and who turns out to be female Sestius: a Roman centurion, brave and dedicated companion on a dangerous quest—though he planned to eventually desert Sabellia: a fierce, knife-carrying Gallic woman, able to make men who assault her deeply regret their act