A Chicago fire investigator attempts to apprehend the arsonist who has set a series of blazes in run-down buildings near the river. He suspects that the perpetrator might be part of the throng of on-lookers that gawk at the firefighters battling the blazes. When a deaf woman is seriously injured in one of the torched buildings, the inspector redoubles his efforts to arrest the firebug before one of his blazes results in death.