Professor Bradley Davison of Queens College is back and this time, he is faced with his most enigmatic mystery. A one-time distinguished professor, Ralph Acquino, is caught plagiarizing and committing other acts of fraud by a graduate student. As a result, Acquino loses everything—his job, his income, his home, and his reputation. Reduced to committing petty crimes to survive, during one incident he commits an act of violence which almost results in an innocent victim’s death. He is discovered, arrested, and sentenced to a lengthy prison term. The arresting officer is Sergeant Marcie MacMillan, soon to be a member of the NYPD’s ‘flying squad’ of homicide detectives. While in prison for twelve years, Acquino swears vengeance upon everyone responsible for the ruining of his life. Upon his release, one by one the bodies begin to show up. On each victim, Acquino leaves a ‘calling card’ in the form of a mysterious number. Stymied by what the police cannot decipher, Chief Mag Goldman calls upon his friend Brad Davison to figure out the meaning of the numbers before the killer strikes again—this time against Marcie MacMillan—now the Commanding Officer of the flying squad.