More like a 3.5, but upgraded for clever plotting and good pacing, although, there were some tiresome redundancies I could have done without.
As for setting, you would have to go far to find a creepier murder venue than an old, Victorian mental hospital, built on Norman, 11th-12th century, foundations! It positively reeks of insanity, which is the whole point of this serial-killer chase!
This is an older book (copyright 1993) and it creaks with age and attitudes. There are only rudimentary computer resources available, they rely on pagers and beepers rather than on cell phones, and DNA comparisons are unknown. It is also riddled with male chauvinism, but the men know they are guilty of prejudice and there is a miasma of uncertainty among the whole police force, of men and women as they struggle to find their way to being true equal colleagues. It is actually fascinating to watch how that social change was wrought over the course of so many years. By 1993, they had come far enough to have accepted women police officers as here-to-stay, but they still had all the old tea-making, weaker sex faint-of-heart, working habits. All of this was consistent through-out the book as it is a product of that time. For those feminists who clamor for "more" justice, they might try to remember how it was less than 30 years ago and consider how far society has come since then.
Back to the book! This is number 2 in a series and having not read the first one, I really began to wonder why it was called on the front cover "A Sergeant Trevor Joseph" mystery, rather than a "Sergeant Peter Collins" mystery, as he was the lead for at least the first half of the book! His one-time partner, Trevor Joseph, is a patient in the mental hospital during the whole length of the book. At first, he is practically comatose with depression and it seems that he will never recover or care enough to actively participate in the growing crime case which he is so perfectly placed to observe. However, his transition from trembling agoraphobe to fully functioning police detective in less than 24 hours is astounding and not really credible! Of course, it is essential to the structure of the book that this metamorphoses takes place in order for him to solve the case. I did find DS Collins the more believable and relatable than Sergeant Joseph, despite his rough edges.
There are bodies galore here, found in gruesome graves and literally, littering the grounds! The killer is well hidden, but I did finger the culprit before the reveal. There were several other secrets "exhumed" along the way and I caught most of those too! None of the plot points were obvious though, so it kept my interest all the way through. I will look for more books by this author.