The Flowers of Vashnoi — Lois McMaster Bujold

Still new to her duties as Lady Vorkosigan, Ekaterin is working together with expatriate scientist Enrique Borgos on a radical scheme to recover the lands of the Vashnoi exclusion zone, lingering radioactive legacy of the Cetagandan invasion of the planet Barrayar. When Enrique's experimental bioengineered creatures go missing, the pair discover that the zone still conceals deadly old secrets.