After manifesting thorned magic and nearly destroying his hometown, Kieren Belltower is summoned to join the Magic Service-an institution in charge of magical affairs-and start an apprenticeship with a high-ranking magician. But instead of the mage assigned to teach him, Kieren is greeted by his haughty and annoyingly handsome senior apprentice Esten, who clearly has more important things to do than chaperone some newbie. Their teacher has disappeared on a secret assignment, leaving Esten's no instructions other than a warning not to trust a soul. But as Kieren's unruly magic proves too dangerous to leave unattended, Esten has no choice but to involve him in the matter.Together they retrace their teacher's last known mission-an investigation into the illegal use of magic and its connection to the devastating phenomenon called the sludge, which has plagued the country for weeks. But as Kieren and Esten grow closer, they uncover a plot that thrusts their lives into danger and threatens to shatter everything they know about magic and the world they were born into.