Silent Ritual by Andrew James Greig

An ear-shattering scream pierces the quiet Glasgow street as a mother stands frozen in her doorway, groceries strewn at her feet. Her son holds a bloodied knife while his father lies dead before him.
As Logan Martin begins his prison sentence for the brutal murder of his father, the eighteen-year-old’s aunt hires private investigator Terlach Paterson. She believes Logan is innocent and wants Terlach to uncover the truth.

Terlach’s visit to the Martin family home yields two disturbing discoveries: a pentagram etched under the carpet in Logan’s sister’s bedroom, and a link to the sinister deaths of their elderly neighbours—a journal with the same ominous symbol lies in the couple’s home.
While ritualistic murders plague the city, bodies placed precisely on an occult pentagram, bound in intricate knots, Terlach and his team unearth the sinister inspiration behind the killings in a mysterious ancient map.
Then, two young women are reported missing, and Terlach fears the worst. He’s inching closer to a killer who is weaving a complex web of murder rooted in Glasgow’s pagan past. But can Terlach stop the twisted soul from carrying out another cruel ritual? This time, one of his own is about to be in grave danger.