Princess Lydia and Lady Dia are planning a state wedding for Mags and Amily. Convinced that such an occasion has disaster written all over it, they take an afternoon and secretly marry with only Amily's father, Herald Nikolas, and all three Companions in attendance.
While serving a shift in Haven's law courts, Mags makes the acquaintance of Linden Pardorry and Tuck. Tuck is a master craftsman who can build anything that can be explained to him. Linden, who views herself as a sort of older sister, has been taking care of him since his mother's death as he isn't entirely capable of coping with the world. Amily discovers that her variant Mindspeech Gift allows her to understand Tuck better than anyone else can. Mags sets up Tuck to work exclusively for the Heralds making things like lockpicks and cleverly hidden grapnel hooks. With her ability to communicate with him, Amily takes Tuck the commissions, including a few for herself and Mags as a surprise wedding gift.
Meanwhile, Amily sets up her own spy network in the noble families. Lady Dia will take in carefully selected applicants from among the pool of poor spinster relations of the noble families to train in her school for handmaidens. Alongside more mundane lessons such as event planning and hair styling, these ladies would be trained to spy for the crown by Lady Dia's husband, Lord Jorthun, who taught Nikolas to be the King's spymaster. Keira Tremainet becomes their first pupil.
Just as everything seems to be going along smoothly, the Menmellith Ambassador shows up with a small escort, all riding horses near foundering. With a ten-year-old king on the throne, the king's cousin Astanifandal stirred up a rebellion in the north of the country. They were found to be supplied with weapons and armor from Valdemar. Not believing that King Kiril could possibly be behind it, the ambassador carried word as fast as he was able, trying to buy Valdemar's government time to find out who was responsible and stop it, before Menmellith's Regency Council declared war on Valdemar.
Believing that the only way these weapons could be purchased was by smuggling undeclared, unusually valuable gemstones from the mines, Mags was sent to investigate, along with Lord Jorthun, Keira Tremainet and one of Mags' street boys, Coot. Nikolas was sent out to investigate the armories that produced the weaponry.
Meanwhile, Amily took care of Tuck, Linden, and Mags' band of street children, one of whom began giving her lessons in roof-running. She also did her best to calm Rethwellan by way of their Ambassador, delaying any action on Rethwellan's part to join Menmellith in a war declaration.
Eventually, the scheme is traced back to a man calling himself "General Thallan" of the Valdemaran Guard. He had subverted an entire Guard outpost, convincing them that supporting the Menmellith rebellion was in the best interests of protecting Valdemar. When the rebellious Astanifandal became king in Menmellith, he would be beholden to Valdemar, eventually signing on as a client state and paving the way to annexation. That would give Valdemar a second, flanking border on its hereditary enemy, Karse.
As the net to capture Thallan began to close, he kidnapped Mags and Amily and retreated to his stronghold, an abandoned Guard fortress. He deduced that their state wedding was another tactic to buy King Kiril more time, so he kidnapped them to prevent it. Thallan also planned to assassinate the Companions in order to remove the Heralds from the equation.
Using their Gifts, some surprises Tuck had made and worked into their clothing, and a bit of unexpected aid from Healer Cuburn, Mags and Amily escaped the dungeon. They convinced the Guardsmen to stop following the madness of Thallan, put down their arms, and let Prince Sedric and his army in the front gate. Thallan was captured and turned over to Menmellith for justice.
The tale ended with Mags and Amily's state wedding.