Michael Kelly, a tough-talking Irish cop turned private investigator, is hired by an ex-flame to tail her abusive husband. But what looked like a bread-and-butter domestic dispute turns out to be more than he bargained for. The tail leads him to an old house on Chicago's North Side. Here he finds a body and what looks like the answer to one of Chicago's most enduring mysteries: who started the Great Chicago Fire of 1871 - and why. As he explores further he is drawn into a web of corruption and intrigue that reaches right to the top. And soon Kelly finds himself in the last place he wants to be - City Hall's fifth floor, where the Mayor of Chicago is feeling the heat and looking to silence any investigations.