The New York Department of Weights and Measures has hired a new chief deputy inspector after the previous one lands in the hospital. The new man is Johnny Cave (James Cagney) a recently retired boxer with plenty of attitude as well as street smarts to do the job. After being on the job for a short time, Cave uncovers a scam, organized by a crooked city alderman and some prominent merchants, to cheat the public out of their rightful goods while the conspirators get rich. Cave must endure pressure from merchants and politicians alike while he attempts to expose the corruption in his department.