Mara Venn has a compact, weather-braced presence, as if she has spent years leaning into wind that never quite lets up. Salt has roughened the skin at her temples and left pale, dry crescents at the edges of her nostrils. Her dark hair is braided close to her scalp and pinned beneath a wool cap, but short coils escape at the nape. She wears a brass tide whistle on a cord, polished bright where her thumb rubs its mouthpiece and green with age in the grooves. In a crowded room her eyes travel first to doors, windows, and the nearest visible waterline, rarely settling on a face until she has counted the exits. She walks with a sailor's careful, rolling balance, even on dry boards, and leaves behind the impression of a person who has already noticed what is about to go wrong.

Mara is decisive when a boat is in danger and stubbornly careful when there is time to think. She has a dry, generous humor with tired workers, but becomes clipped and overbearing when someone treats the river as scenery. She wants people to trust her judgment, yet distrusts her own instincts whenever a decision resembles the one she made during the Long Thaw. In private she is tender toward children and the injured; in public she hides that tenderness behind lists, schedules, and blunt orders.

Mara was raised around Bellwether Quay's ferry sheds, the daughter of a rope-maker who taught her to tell a sound line from a doomed one by touch. At nineteen, she took a place on the river ferry and learned the crossing by its smells, eddies, and shifting banks. During the flood known locally as the Long Thaw, she followed her captain's order to hold the boat at the near bank while the current rose. A second boat, carrying her younger brother and several stranded families, broke loose and vanished downstream. Mara survived, but she has never forgiven herself for obeying an order instead of trusting her own reading of the water. She became harbormaster to keep such decisions from being made carelessly. Now the ferry route to the far bank is blocked by a wrecked barge and a fresh, unpredictable current. Food and medicine are spoiling across the river. Mara has hired the party because the quay crews are exhausted, the available boats are too small for the job, and she cannot spare the few steady hands needed to keep the town supplied. She is in a running dispute with the local grain factor over who should pay for the salvage, and she still sends a small portion of every wage to her brother's surviving daughter, who believes her father died on a different stretch of river.