A Case of Closure - Joseph A. McCaffrey - Bog

In 1978, Margaret Thode, a high school senior from Rock Island, Illinois, was murdered. The act was vicious, personal, and vile. Her murder was never solved.
The crime haunted her girlfriend, Agatha Pruitt, who went on to become a research librarian at the University of Iowa. Agatha, now newly retired and back in Rock Island, re-opens the murder case long abandoned by the police. She herself meets an untimely demise shortly thereafter.
Agatha's brother calls upon Bertrand McAbee to undertake a private investigation into his sister's murder. Reluctantly, the aging McAbee consents. Once again, McAbee needs to rely on his longtime loosely connected comrades to assist his agency, ACJ, in bringing a killer to justice.

McAbee finds the thread that links the two murders and concludes that the murderer of both women is still at large, rattled by Agatha's inquiries. As McAbee's attention shifts to the 1978 cold case, among many obstacles he must deal with is the chief homicide investigator of Rock Island who detests McAbee for his relationship with Augusta Satin, his pillar of strength, confidant, and more at ACJ.
Leads are few, as McAbee must deal with an assortment of characters to gain a foothold. After many dead ends, he finally catches a break. But it puts him up against a professional killer mentored and protected by one of the world's greatest powers.