The Crucified Lady — Robert McDowell

Inspector Jeremy Adams is assigned by Scotland Yard to investigate the horrific murder of a reclusive aristocrat.
Although helped by local police sergeant Mary Bright, his job is complicated by an ambitious local detective with connections in high places.
A second death, hundreds of miles away, is thought to be suicide, but the inspector believes otherwise, and uncovers a secret that makes him think both crimes have been solved.
They have not, and the inspector realizes he must unravel multiple plots with a common goal, that causes a tragedy of 'biblical proportions'