Synopsis of the plot of McDermid's The Mermaids Singing
JKR was condemned , entirely incorrectly, for the killer in her last book being trans. One might have hoped, given McDermid actually did have a trans murderer that McDermid might have spoken up for Rowling. I don't recall seeing her doing so.
In the fictional English city of Bradfield, men are being abducted and tortured to death using brutal medieval techniques. The bodies are then found in areas frequented by gay men and women. The police reluctantly recruit a criminal profiler, Dr. Tony Hill. He joins forces with Detective Inspector Carol Jordan, for whom he develops complicated romantic feelings. Dr. Tony Hill has problems of his own, including a mysterious woman named Angelica who frequently calls him for phone sex. As Tony becomes increasingly involved in the investigation, it becomes apparent that the killer is seeking Tony as the next victim. The killer is revealed to be the anonymous caller Angelica, a transgender woman who kills men that do not return her affections. When kidnapped, Tony figures out her weakness (her desire to be loved) and uses it to avoid being tortured and murdered