DCI McNeill, at the helm of Edinburgh’s Serious Crime Unit, is accustomed to confronting the city's darkest secrets. However, a body discovered in an impoverished tower block, marked with Celtic symbols, propels him into a case that challenges even his seasoned instincts.
But the victim's link to the city's treacherous drug scene and a notorious crime lord complicate matters. With diverging leads and mounting pressure, Mac seeks the expertise of Dr. Clio Wray, a scholar in ancient symbology.
As another body emerges and unsettling connections to Mac are revealed, the case spirals into uncharted territory. Then Clio unearths a chilling clue hinting at a third victim and Mac has no choice but to follow.
Drawn into the labyrinthine depths of a fractured mind, Mac is about to face an explosive challenge that could cost him his life.