Grandmother's footsteps - Carol Smith

The cold-blooded butchery of a mother and her daughters triggers a wave of outrage in the media. Though not immediately obvious because they are so widely-spaced, this is just the latest in a series of bloody murders.
It takes the patient persistence of cartographer, William Huxley, to sense a link the police have missed and slowly unravel the puzzle. Stuck at home with the two-year-old Morwenna while his high-flying wife, Edwina, plays with fire, William, the puzzle-solver, slowly assembles the pieces, aided solely by a cub reporter and the valiant cleaning lady, Mrs. P.
When a prominent public figure is hacked to death, events take a sudden sharp curve for the worse. Particularly when it rapidly becomes clear that William is the next intended victim.