The Roubaud Connection. Genevieve Lenard, #12

Brutal murders. An ancient treasure. A rogue state. A young acquaintance of nonverbal communications expert Doctor Genevieve Lenard begs her to look into the disappearance of his friend. When the friend's tortured body is found in a forest outside Strasbourg, the case leads Genevieve and her team to the body of a second victim with many unusual secrets-a forged masterpiece the least surprising of them all; an ancient treasure shrouded in mystery the most intriguing.
While Genevieve is frantically searching for a motivation behind the murders, more tortured bodies are dumped in the forests surrounding the city-all connected to her young acquaintance. And the moment she discovers that the evidence points to a rogue state, her young acquaintance also disappears. Without knowing who the killer is and why he's torturing his victims, there will be no stopping him. Or saving her friend from vicious suffering and eventual death.