He was surprised when he found the body. He was even more surprised when Farmer Jane got off her tractor, came down from the field, cut the fly off the fly rod and took some hairy mess out of the mouth of the dead man. Even so, he said nothing about it to the police chief or the man harassing the chief. After the authorities had taken the body away, Farmer Jane “Junior” expressed her appreciation. She also said he could do her a favor by taking the hairy thing along with him as he was leaving.

He, Ned Oglivie, “Dog” was heading out. He had intended to fish the stream that ran by Black Earth, but he hadn’t expected the bodyand the baggage that came with finding it. There were other streams to fish. By sunrise he could have his old Cruise Master north to the Big Two-Hearted River.

The body he found was Jake Jacobs, an environmentalist who had been on a mission. He had wanted to maintain the Black Earth Creek as a trout stream by stopping the agricultural runoff and removing the dam that held back a defunct mill pond. He had made enemies. Junior’s father had made a threat against Jake at a public meeting, saying he would cut off the ponytail and stuff it in his mouth. That explained why Junior had removed the hairy thing from Jake’s mouth and pawned it off on Dog. She had involved the Dog in her crime. And he wasn’t as sure as she was that her father was innocent.

The more Dog learned about the Black Earth situation, the more he thought he could help. Though he had spent three years as a trout bum trying to escape his memories, he had previously operated a security company. For the first time in years, he was also interested in a woman. Melvina O’Malley, Junior, had an attraction that he couldn’t quite grasp. She was a farmer, an optimist and her father’s caretaker, as he had dementia. She seemed to think that if Dog helped, things would turn out all right.

Bud Bjorstad was the mayor of Black Earth. His son was the police chief. Since Mayor Bud was calling the shots, they were known locally as Bud and Bud Light. Bud Senior had developmental property that fronted on the mill pond, and he had no interest in seeing the “lake” removed. But he had been chairing a meeting at the time Jake was murdered. The time was known since Jake had a Yellow Sally fly on his rod, and everyone knew that the Sally hatch was at 8 p.m.

As one might expect with a book named” The Nail Knot,” a little used nail knot becomes a very important clue. Dog believes that the leader on Jake’s fly rod was tied at the scene of his death, and it was done with a perfect nail knot. Not everybody could do that, and that should limit the number of suspects.

One of the people who could was the person who tied the unique yellow sally flies. Dickie Pee (there’s a story behind that name) would have to negotiate a wheelchair. Part of the mystery was how a relatively young man like Jake could be drowned in a creek. That was not something that could be accomplished by a person bound to a wheelchair.

Though this is a relatively small book, there are several additional characters and incidents. It is indeed a mystery. I believe this is the first mystery written by Wisconsin author John Galligan, who also writes the Bad Axe series.