Wallace is a soft-bodied, middle-aged human with a broad, pale face that seems permanently surprised by the behavior of his own inventions. His thick, square jaw works side to side when he concentrates, and his large, slightly buck-toothed grin arrives before his explanations do. His grooming is unexpectedly meticulous: hair combed into a precise side part, moustache trimmed to matching points, and cuffs brushed clean even after a workshop accident. He moves with the careful, testing tread of someone who expects the floor to do something odd. People remember the cheerful grin, then notice how closely he watches every hinge, paw, and person in the room.

He is hospitable and chatty when someone is curious, but becomes exacting when a device is handled carelessly. He genuinely enjoys praise, yet distrusts grand promises. In a crisis he turns brisk and unshowy; afterward he may fuss over everyone with tea and spare buttons rather than discuss how frightened he was.

Wallace learned precision in the municipal clockworks, where he spent his youth repairing tower mechanisms and eating lunch beside the gears. His most important early partnership began when he built a small brass hound to keep him company during night shifts. The hound, Picket, learned to fetch tools, bark at faulty pressure valves, and stubbornly refuse commands that would put Wallace in danger. Years later, during the disastrous North Sluice flood, Wallace's hurried pump design failed. His apprentice, Tamsin, stayed behind to open the manual gates and saved a crowded riverside ward; Wallace escaped with a shattered reputation and a conviction that no device should be trusted without a person ready to intervene. He rebuilt the sluice system with public inspection panels and gave Tamsin credit, though she left to work elsewhere. Now he runs a cramped repair shop and prototypes civic machines, while the municipal works committee pressures him to sell his latest design to a private contractor. Tamsin still sends terse notes about the repairs she makes to his old work, and Wallace keeps each one.