The sheriff commissioned his own investigation of the investigator, accusing him of serious crimes that, he said, had nearly caused an innocent man — his officer — to be charged with murder. He embedded his accusations in the public consciousness through a cascade of press releases, phone calls, letters, interviews and online posts. He sent his findings to state law enforcement officials and the F.B.I. As a result, Agent Rodgers’s own employer and later a special prosecutor began investigating him. He was placed on administrative leave, forced to surrender his badge and gun, barred by his agency from publicly defending himself.

In April, I returned to St. Augustine to report on this second act of a drama that, over seven years now, has sown deep scars in this community by the sea. It has divided the law enforcement establishment, not to mention the family of Michelle O’Connell. It has been reviewed by one state attorney, three special prosecutors and four medical examiners, and is debated still in the local press, on the beaches and in the bars. It has, in short, become the stuff of Florida noir, featured in a documentary on Netflix, in People magazine and on television shows like “Dr. Phil.” “I’ve never seen anything like this before,” said Dr. Frederick Hobin, who performed the original autopsy.

On this trip, I approached several of the central players who had declined to be interviewed before. I had new questions, based on my review of thousands of documents not available when I first reported on the case.

Sheriff Shoar had promised to spend the rest of his career holding Agent Rodgers accountable. But what I came to learn was that the sheriff had tried to destroy the investigator with accusations that were often nothing more than innuendo and unverified rumors. Even so, they went virtually unchallenged for years.

In the end, the sheriff did not achieve his goal of seeing Agent Rodgers sent to prison, charged with a crime or even fired from his job. But he did accomplish something else: He diverted attention away from his office’s own botched investigation, the spawning ground for so much of the anger and conflict that followed.