The following version of the novel was used to create this study guide: Buchanan, Greg. Sixteen Horses. Flatiron Books, July 20, 2021. Kindle.

In the crime novel Sixteen Horses by Greg Buchanan, detective Alec Nichols is escorted by an area farmer to see sixteen horses’ heads found buried on his property. The investigation of this crime led Alec and Cooper Allen, a forensic veterinarian called in to help, to discover a chain of connected crimes including blackmail, murder, poisoning, and suicide. When the case came to its gruesome and surprising end, Cooper discovered she had been negatively impacted by what she had observed and what she discovered about herself and others.

During the course of the investigation, Alec and Cooper determined that two people had been blackmailed into helping with the killings of the horses. Charles Elton, who owned a riding stable, was the owner of many of the horses killed. Later, Charles received a note ordering that he kill himself to keep him from telling anything he knew to the police. Kate, a veterinarian, was also blackmailed and also died by suicide. Before she died, she called Cooper and told her that the man had blackmailed her into helping him with the horses. She believed they were only stealing them. She did not realize they would be killed until she heard them screaming in the back of the van.

Meanwhile, police officers and others who had been at the scene where the horses were found began to get sick. The horses had been poisoned with anthrax that was intentionally placed near the horses’ heads. Alec was among those who were hospitalized. Right before Alec was hospitalized, he wrecked the car in which he and his son, Simon, were riding. Alec wandered away from the car before Simon regained consciousness. By the time police found Alec’s car, Simon was gone. It was believed he was either dead or had been abducted.

Cooper did not get sick because she had been vaccinated against anthrax. A representative from the government’s health services took Cooper to an island where a man lived who had suffered with mental illness. The depth of his illness was not known until he set fire to the buildings on the island, killing his entire family with the exception of his youngest daughter. That girl never spoke about what she had experienced. Ada explained that the man had sowed anthrax in the marshy areas of the island. It was believed that was from where the anthrax placed around the horses’ heads had come.

Additionally, fifteen dead crows were found in a pit on the island. Each of the crows had a copy of a letter pushed down its throat. Alec’s fingerprints were on the wrappings of these letters. Later it was determined Alec’s prints had been lifted from another place and put on the wrappings intentionally. It was believed these letters were a sign that the crimes were focused on Alec.

As Alec’s condition began to improve, Cooper slowly began to involve him in the investigation again. Investigators asked him about a broken mirror found in his trash, and if he had been abusing Simon. They asked him about a phone number they found on his kitchen table. The number belonged to Grace Cole, the wife of the farmer on whose property the horses had been found. The farmer and his daughter, Rebecca, claimed Grace had left Ilmarsh a year prior and gone to Portugal. Alec had intended to call Grace, but never followed up.

As Alec recovered, he called Grace, but did not receive an answer. He connected with her on social media and became convinced that she was the one who was holding his son captive. Alec received a message from Grace asking him to meet her near a lake on the farm where she once lived. When Alec arrived, he found Simon, who appeared to be traumatized.

Meanwhile, Cooper discovered Alec had gone to the lake and followed him. She was hit over the head and almost killed by her attacker, but she fought back and killed him when she pushed him backward onto some rocks, fracturing his skull. At first, she believed her attacker was Alec because he was wearing Alec’s clothes. It turned out to be Simon. Cooper found Alec’s decapitated body in a crate close to the lake.

Based on evidence found on a camcorder, divers pulled the bodies of Rebecca and Grace out of the lake. Rebecca, who had once dated Simon, had died of strangulation recently. Grace had been dead nearly a year, since the time her family claimed she had been missing. Information on the videotape suggested that at Simon’s encouragement, Rebecca had been giving her mother more of her blood thinner than she was prescribed, hoping that it would make her too weak to abuse Rebecca as Grace had been doing. Instead, her family found her dead one day. It was unsure if the death was intentional or accidental.

One year later, Cooper visited a therapist to try to overcome her self-doubt and self-loathing because she could not stop Alec’s death and she believed that she was responsible for killing Simon. She was called with a job offer. However, she feared that working another case would only strengthen the ghosts she sensed in her consciousness. She believed that to be happy she needed to spend time with her family, away from her job. The reader does not learn if Cooper takes the job or if she declines it and goes to see her family.