The Sacrament of Poison

This is an Apple Books audiobook narrated by a digital voice based on a human narrator.

While field testing new laboratory equipment, Max Fite uncovers evidence of long-concealed homicides. He recognizes the names of the victims because he's visited their graves often.

As evidence leads him and his colleagues to suspect the worst, he teams up with Lauder Gray, a private inquirty agent, to follow clues that lead him to an unexpected conclusion.

The question isn't only 'who did it?' but 'HOW?'