Lady Sandrilene fa Toren is locked away in a dark room with a fading oil lamp. She was magically hidden in this storeroom days ago by her nurse, who was then murdered moments later by a mob bent on destroying everything infected by the fierce plague that killed Sandry's parents. Sandry, even though she knows there is no chance of anybody finding her, is concerned about the flickering lamp because she is afraid of going crazy in the darkness. Unknowingly doing her first piece of magic, Sandry traps the remaining light in a simple braid. A powerful seer Niklaren Goldeye finds her and lets her out. Niko takes her to Winding Circle in Emelan.
Trader Daja Kisubo is the lone survivor when her family's ship is destroyed in a storm. She floats on the water for days, surviving only because she finds a suraku- a survival box full of food and water from the ship. When Niko finds her, they go to the Trader Council so they can decide Daja's fate. Because Daja is the only survivor of her family, the declare her trangshi or outcast- the worst sort of bad luck. As trangshi, she is forbidden to speak, touch, or write to other Traders. Niko is outraged at the council's decision and conducts her to Winding Circle.
Roach (later named Briar Moss) is a "street rat" in Hajra, Sotat. His mother died when he was four; he was then taken in by the Thief Lord, the leader of the gang Lightning. Each time Roach was caught, an "X" was tattooed onto the web of skin between his thumb and forefinger. This happened twice, until he was caught a third time. As Roach was being sentenced to the docks, Niko stopped the judge and convinced him to be allowed to take Roach to Winding Circle. Roach also got to pick a new name for himself; he chose Briar Moss because of his curiosity and experience with plants.
Trisana Chandler is from a merchant's family. She was passed from relative to relative because strange things occurred when she was around: hail, lightning, and storms. Never staying long in one house, she never had a real family. Out of relatives, she was finally brought to Stone Circle Temple by her parents and left there, where she wreaked more havoc still. The temple's dedicate superior pleaded with Niko to take her to Winding Circle, which he did.
The four kids are all brought to Winding Circle Temple in Ememlan, where they do not fit in. Daja is secluded and ignored because she is a Trader, Tris wreaks havoc through weather when girls make fun of her, Briar threatens other boys with knives, and Sandry is caught looking at the looms too much. They are all taken to Discipline Cottage, an isolated cottage for children who don't fit in. They are overseen there by Dedicate Lark, a kind and gentle thread mage, and Dedicate Rosethorn, a sharp plant mage.
At Discipline Cottage they learn they have magic, which none of them knew about. While they all practice meditation, each of the four is matched with a main teacher to guide them through their magical learning. Sandry works with Lark, learning to weave and spin. Tris studies with Niko about weather. Daja is taken under the wing of Dedicate Frostpine, the greatest smith mage. Briar works with Rosethorn in her garden and workshop. They each grow closer together and stronger in their magic.
During the course of the book, there have been tremors all summer. Near the end of the book, a big earthquake comes. Sandry, Tris, Briar, and Daja are trapped in a cave and the ceiling is falling. Through their magics, they try to protect themselves from the biggest quake yet to come. To get enough power, Sandry weaves the fours' magics together, making them stronger. This allows them to ride out the earthquake. At the very end of the book, Tris, Briar, and Daja present Sandry with a light filled crystal to help her conquer her fear of the dark.