The following version of the book was used to create this study guide: Krueger, William Kent. Lightning Strike. Simon and Schuster, Inc., New York, NY, 2021. Kindle AZW file.

In 1989, Cork O'Connor walks around Aurora as the newly-elected sheriff of Tamarack County, Minnesota. Almost immediately, he encounters a drunk man who is angry that an Indian has taken the office. Cork and a deputy discuss the clock on the courthouse, which has not worked since 1963 when a shootout occurred. Cork's father Liam, who also served as sheriff, was killed in that gunfight. Cork finds a moment to take a seat across from the courthouse and think back on his past.

In 1963, Cork is 12-years-old. He and his friend Jorge Patterson hike the 10 miles from Aurora to a place known as Lightning Strike. It was a mining camp struck by lightning years earlier. The Ojibwe people felt it was divine retribution for decimating a place the Indians held sacred. The boys note the smell of something foul and discover the body of Big John Manydeeds, a member of the Ojibwe tribe, hanging in a nearby tree. When Liam arrives with deputies, he notes two whiskey bottles at the scene and jumps to the conclusion that Big John gave in to his demons and committed suicide. At Big John's house, Liam finds more whiskey bottles, supporting that ruling. He orders a toxicology report but decides to forego the autopsy, especially considering the body had been hanging for days before Cork found it.

Liam is soon beset by objections from the Indian community, all insisting that Big John had given up alcohol long ago and someone killed him. Liam continues his investigation though he later admits that many of his early conclusions are made through the haze of prejudice. Liam's wife is half Ojibwe, but Liam soon discovers he cannot really know what it is like to fact the kind of prejudice Indians have endured, especially at the hands of white officials.

Billy, Big John's nephew, returns to town and renews his friendship with Cork. Billy and Cork return to Lightning Strike where Billy is certain he feels Big John's spirit and Cork sees an apparition. They seek out the advice of an elder in the community who advises them to “follow crumbs” of information in their quest for the truth. While Liam is conducting the formal investigation, Cork sets out on his own with the help of Billy and Jorge. Both Liam and Cork are diverted by dead end clues and unanswered questions.

Eventually, they discover that Big John was having an affair with Mary Margaret MacDermid, the wife of wealthy mine owner Duncan MacDermid. Duncan has reason to hate Big John, but he is also at odds with Nick Skinner. Skinner, Duncan's attorney, is trying to build a resort hotel in a town Duncan does not want to see changed. Big John had a somewhat stormy relationship with his half-brother Oscar who has access to the drug found in Big John's body. The situation is muddied when Duncan attacks Mary Margaret. Mary Margaret kills Duncan, putting an end to any chance he can confess.

The body of a 15-year-old Ojibwe girl turns up in the lake. Liam and Cork believe the two cases must be connected. What they eventually discover is that three local men took Louise to a camp on the lake. Big John happened to pass by and showed concern for the girl. Later that night, Louise fell and hit her head and the three men – Nick Skinner and brothers David and Ben Svenson – tied her to a rock and sank her body in the lake. When Big John returned to check on Louise, the three men killed him as well, staging it to look like suicide. David confessed; Liam killed Ben; and, Nick was put in prison.

A year later, Cork and Colleen were outside one evening when they heard the sound of firecrackers. One of Liam's deputies raced to their house with news Liam had been shot. At the hospital, they waited while Liam went through surgery, but he never regained consciousness. In his grief, Cork was furious that his father put himself in danger to save someone else. Cork pledged he would never wear a badge.