Very Different Mystery

Finished March 6
Still Waters by Nigel McCrery
This is a very different mystery novel. Main character DCI Mark Lapslie gets called off sick leave when a traffic accident brings a body to light. Mark doesn't understand why he would be linked with this case. He's been off on leave due to his acute synaesthesia. Mark's version of this means that sounds set off tastes for him. The sensory overload at work was too stressful, and the condition has even affected his marriage.
Both voices and other sounds trigger the tastes and sometimes they are extremely unpleasant. Even when not, they don't always go together well.
The body that has come to light has been dead around 9 months and has had some fingers chopped short after death. It also appears that the victim was poisoned. Lapslie is intrigued by the case and despite some discouragement from his superiors keeps doggedly on, following every clue he has.
We also see some of the story from the murderer's viewpoint, a woman who ingratiates herself with elderly isolated women and then poisons them and assumes their identity.
How is Lapslie connected with her and will he be able to find her before she finds and kills her next victim. This is a very interesting plot and although very violent, makes a great and engrossing story.