EIGHTEEN-YEAR-OLD AIHUI YING dreams of becoming a world-class engineer like her father. But after his unexpected murder, a heartbroken Ying is determined to discover why anyone would threaten a man who ultimately chose a quiet life over fame and fortune. Left with only a journal of her father's engineering secrets and a jade pendant snatched from the assassin, Ying follows the trail to the capital and the prestigious Engineers Guild—a place that harbors her father's hidden past. Disguised as her brother, Ying manages to infiltrate the male-only apprenticeship trial with the help of an unlikely ally—Aogiya Ye-yang, the nation's taciturn eighth prince. With her father's renown placing a target firmly on her back, Ying must stay one step ahead of her fellow competitors, the jealous guild masters, and the killer still hunting for her father's journal. Complicating everything is her increasingly tangled relationship with the prince, who has mysterious plans of his own. The secrets hidden within the guild can be as deadly as the weapons they build-and with her life and the country's future at stake, Ying doesn't know who to trust. And can she avenge her father if it means going against everything he stood for?