Sada is a lean, weather-tough human woman with a pale scar running across one cheek, thin as a chalk mark against her brown skin. She stands with her weight forward on the balls of her feet, as if the earth might shift under her at any moment. In a room, her eyes go first to the floorboards, then the exits, then the people. Her reed-brown hair is braided close to her scalp and tied with a strip of blue sailcloth. She moves with short, sure steps, placing each foot as though testing a hidden plank. People remember the small, deliberate tap of her knuckle on every piling she passes. Unexpectedly, she keeps a tiny, neatly folded paper theater tucked inside her coat and makes new cutout figures when she cannot sleep.

Sada is wary of confident plans but generous with people who admit what they do not know. She is brisk and unsentimental while guiding a group through danger, yet patient with frightened children and newcomers. In ordinary company she makes dry jokes; when reminded of the walkway collapse, she becomes fiercely practical and refuses comfort that sounds like absolution.

Sada grew up in Reedcut, where her mother repaired walkways and her father ferried fish baskets between reed islands. She learned the marsh by sound: the suck of mud, the thin complaint of a loose board, the hollow note of a piling eaten from within. When she was twenty, a flood swept away a walkway during a crowded market crossing. Sada heard one support groan but dismissed it as ordinary strain; her younger brother, Kesi, was among those who fell into the current and was never found. Since then, she taps every piling she passes and refuses to hurry across a structure she has not checked. Her old friend Thesi, a net-mender, thinks Sada blames herself too much; Boro, the settlement's ferry-master, thinks she costs him time and customers. A new stretch of walkway is being built over ground Sada believes is sinking, and the builders are ignoring her warnings. She guides travelers for a living, but keeps returning to that construction site, listening for the sound she fears she will recognize.