A mystery. The son of a retired Chicago Police detective is murdered for no apparent reason and Johnny O'Rourke goes back to Chicago to find the murderer and extract his revenge, and soon finds out that there are more than one that may profit from his son's death. A step by step investigation uncovers clues that lead Johnny and his new partner to the culprits. All the clues are clear in the text and the Reader is challenged to solve the mystery together with Johnny O'Rourke and Carol Mackenzie.