The following version of the book was used to create this study guide: Cleeves, Ann. The Heron's Cry. St. Martin's Publishing Group, New York, NY, 2021. Kindle AZW file.

Matthew Venn is the Detective Inspector called to the scene of a murder at Westacombe, a farm that has been renovated by wealthy financier Frank Ley. Frank has remodeled the barn and rents out two small apartments and work spaces to artists Eve Yeo and Wesley Curnow. The victim is Nigel Yeo, Eve's father. Eve is a glass blower, and someone killed Nigel by stabbing a piece of Eve's glass into his neck. A few days later, Wesley is found murdered in his second studio space at a place called the Woodyard, managed by Matthew's husband Jonathan. As the investigation continues, Frank is found dead of an apparent suicide. By the time Matthew's team figures out what is going on, Eve is also missing.

Matthew is fairly new to the job and is still working on making his team efficient and effective. The two main members are Ross May and Jen Rafferty. Like Matthew, both are juggling the demands of police work with their home lives. One of Matthew's biggest challenges is keeping his work life and professional life separate, a bigger challenge because Jonathan is so outgoing and social.

From the beginning, the facts are present but difficult to add up. Nigel had been called on in his official capacity with a community health group to figure out where the medical community dropped the ball by releasing a young man named Alexander Mackenzie from the hospital only to have him die a few hours later. Apparently, the man jumped from a cliff to his death. Nigel died before he could further investigate.

The case is complicated by the discovery of a website that is supposed to provide support for those suffering from depression. However, it is actually manned by someone called the Crow who provokes people into killing themselves. Alexander had been on that site, which supports the idea that he had committed suicide. Another victim of the site is Frank, who overdoses with the idea that he has not used his money to help people as he should have. Frank is just a complication of the main case, however. When the Crow's identity is revealed, he turns out to be a health professional who has gotten addicted to the power of controlling life-and-death decisions.

Matthew leads the investigation, but it is actually Jen who is able to put the facts together to understand the truth. She realizes that all the deaths go back to Alexander who had not committed suicide as everyone believed. His sister Janey, tired of the drain Alexander's chronic depression has on the family, pushed him off the cliff to his death. Nigel found Janey's writing – her way of making sense of the situation and a half-formed plan to make it into a book. Janey killed him to keep him quiet. She then killed Wesley because he saw her driving Nigel's car away from Westacombe. When Eve begins to put facts together, Janey plans to kill her as well. However, she must leave that task in the hands of her father, George. Matthew and Jen catch George before he kills Eve.