Measure of Dissent. The Torian Reclamation, #4

A fool assumes his allies are immune to treason's seduction Three years after the first Ossurian War, the Erobian Alliance begins to fracture when one of its most powerful members commits baffling acts of dissention. In an attempt to diffuse a precarious hostage situation, the Torian High General turns to his most effective tool: the prominent Earthling Brandon Foss. Brandon is reluctantly thrust into a high stakes game of interstellar diplomacy which tests his gamesmanship as well as his battle skills in an effort to prevent an all-out war between three star systems.
But he may already be too late. Unfortunately, far-off star systems aren't the only place where the flames of discord are kindled. The twin planets of Tora enter into a decisive struggle as Belle-ub, the red Sheen leader who has usurped control of Amulen, shows his true colors in an attempt to take over Banor as well. Few see him for the threat he actually is. A violent struggle between the two Sheen factions ensues, which inadvertently entangles Derek-a man only trying to return to his hippie roots-who must now face his own defining test of character. All the while, something mysterious begins happening to the Torian humans.
Something that might even explain much of the burgeoning strife in the Erobian Sphere. Consequently, their list of enemies begins to grow. It's a shame the only ones who don't seem to know about it are the humans.