When their aunt Finna misses their father's funeral, fourteen-year-old twins Colm and Clíana know she has to be in trouble. Finna finally appears with an explanation: she's developed an illata, a unique magical power, and she's used it to become one of the city's best bounty hunters. At least, until a few weeks ago, when a powerful criminal underlord finally got the better of her. Now, he's marked her as one of his own. Finna promises the twins that she can handle it, but they know she's lying.

Certain he can save her from the underlord, Colm follows Finna back to the city, while Clíana chases after them as soon as she realizes her brother's gone. However, Colm's attempted rescue goes awry once he steals a mysterious pair of dice, and he must escape from the underlord's thugs himself. Clíana, meanwhile, sets out to recruit the help of a wizard fluent in the magical language of Alchema. Her search introduces her to an elite, exclusive world, a world she finds both intriguing and impossibly beyond her reach.

As both twins move toward finding Finna, and each other, they soon realize they've stepped into a world, and a mystery, bigger than they ever imagined-a world of dueling magical fates.