Betrothed since childhood to the prince of Mynaria, Princess Dennaleia has always known what her future holds. Her marriage will seal the alliance between Mynaria and her homeland, protecting her people from other hostile lands. But Denna has a secret. She possesses an Affinity for fire—a dangerous gift for the future queen of a kingdom where magic is forbidden. Now, Denna must learn the ways of her new home while trying to hide her growing magic. To make matters worse, she must learn to ride Mynaria’s formidable warhorses—and her teacher is the person who intimidates her most, the prickly and unconventional Princess Amaranthine—called Mare—the sister of her betrothed. When a shocking assassination leaves the kingdom reeling, Mare and Denna reluctantly join forces to search for the culprit. As the two become closer, Mare is surprised by Denna’s intelligence and bravery, while Denna is drawn to Mare’s independent streak. And soon their friendship is threatening to blossom into something more. But with dangerous conflict brewing that makes the alliance more important than ever, acting on their feelings could be deadly. Forced to choose between their duty and their hearts, Mare and Denna must find a way to save their kingdoms—and each other.