Return of the Seraph

Hundreds of years in the future, Earth becomes uninhabitable, and humanity is forced to move to another planet to survive. But this other planet already has intelligent life, a race called the seraph. Humans and seraph have a war over control of the planet, and humanity wins, taking three seraph captive for scientific study.
Several hundred years later, Zack Branford performs a routine inspection of a government facility containing a captive seraph. But everything goes wrong when the seraph escapes, and Zack is recruited to recapture it.
How did the seraph escape? Can Zack recapture it in time? Find out in this thrilling science fiction story.