The Milwaukee Police Department was organized in 1855 with a determined chief, seven pugnacious officers, and little money. The department grew to 21 men by the start of the Civil War in 1861. Law enforcement in the city soon earned the national reputation for honesty, integrity, and fairness it has enjoyed into the 21st century. The Milwaukee Police Department was first in the country to establish a formal officer training school, police bomb disposal vehicle, and "talking squad car." Nefarious criminals handled by the department include the foiled presidential assassin John Schrank, the serial killer Jeffrey Dahmer, and characters with quaint nicknames like "Cat-eye Lil" and "Kelly the Choker."

Kelling, who has studied policing for over forty years, explores the history of policing through the story of the fascinating changes in the operations of the Milwaukee Police Department in the twenty and twenty-first centuries and what it portends for the future.

A bomb explodes in a police station, killing nine officers and a civilian. Those responsible are never caught, but police, press and public are quick to condemn a group of eleven immigrants. This story could have been ripped from today's headlines. In fact, it comes from a 1917 case in Milwaukee, Wisconsin; a miscarriage of justice examined for the first time by Dean Strang, the lawyer whose passionate defence of alleged murderer Steven Avery was at the heart of the hit Netflix series Making a Murderer. Days after the explosion, the eleven suspects went to court on unrelated charges. The spectre of the larger, uncharged crime haunted the proceedings and against the backdrop of the First World War and amid a prevailing hatred and fear of immigrants, a fair trial was impossible. In its focus on a moment when patriotism and terror swept the nation, Worse than the Devil exposes broad concerns that persist today, and failures in the American justice system that will resonate with anyone who has followed the Avery trial.