After the long journey to the Western Khaganate, Cui Buqu and Feng Xiao find their diplomatic efforts stymied when they are accused of murdering a Göktürk prince. Thinking on his feet, Cui Buqu requests a single day to crack the case and clear their names. Yet to everyone's surprise, the crafty chief of the Zuoyue Bureau offers himself as hostage, leaving the investigation-and his life-in Feng Xiao's peerlessly beautiful hands.

Now Feng Xiao faces a difficult choice: watch his rival perish in the desert or risk his own life in pursuit of the true killer. Time is running out, and unsettling forces are at work within the Western Khaganate. Yet Feng Xiao can't shake the feeling that Cui Buqu may have one final card to play-one that could reveal the truth before it's too late.