Nalia is a short young woman with soft, warm-brown skin, rounded ears, and an alert face that seems permanently caught halfway through asking a question. Her bright hazel eyes dart between rooflines, hands, and doorways as though the whole city is presenting a puzzle she has almost solved. She balances easily on one foot when standing still, but moves in quick, careful starts, testing each stair before trusting it. Her neat coat sits a little too squarely on her narrow shoulders, and its many secure pockets make her silhouette look oddly architectural. A tiny pressed sprig of rooftop thyme rests beneath the glass of a keepsake locket, an unexpectedly tender memento for someone who maps alleys and escape routes for a living.

Nalia is watchful but easily flustered by direct attention, and she is more decisive than her bewildered expression suggests. With strangers she hedges every claim; under immediate pressure she becomes startlingly clear and practical. She cares fiercely about overlooked neighbors, yet finds it easier to plan their escape than to tell them she is afraid. Praise makes her suspicious, while honest disagreement tends to bring out her dry humor.

Nalia grew up above her mother's rain-gutter repair shop in the close-packed district locals call Sootstairs, named for the soot-blackened steps that once led to a long-dead kiln trade. As a child, she learned the roofs by following her older brother, Toma, who carried messages between workshops. During a winter flood, a blocked drain sent water through three tenements. Nalia had noticed the warning signs days earlier, but her maps were dismissed as a child's scribbles. When the wall gave way, she and Toma guided neighbors through a roof passage; Toma stayed behind to free a trapped family and was swept away. Since then, Nalia has turned her anxious attention into careful survey work, drawing routes that can save people before the city notices danger. She rents a narrow room above a tea seller, sends most of her pay to her mother, and quietly updates maps for the neighborhood's tenants. Her former mentor, Master Pell, wants her to sell her latest drainage survey to the wealthy council, while Toma's daughter, Iri, wants Nalia to stop treating every rooftop like a memorial. A new crack has appeared beneath the old cistern, and Nalia suspects the same officials who ignored her first warning are hiding another failure.