The Garden of Evil - David Hewson

In a hidden studio in an area of Rome, where the Vatican liked to keep an eye on the city's prostitutes, an art expert from the Louvre is found dead in front of one of the most beautiful paintings that Nic Costa has ever seen – an unknown Caravaggio masterpiece. But before long tragedy will strike Nic far closer to home. The main suspect's identity is known, but he remains untouchable – protected in his grand palazzo by a fleet of lawyers and a sinister cult known as the Ekstasists. If Costa and his team can crack the reasons for the cult's existence, he may well stand a chance of nailing his wife's killer. But the mystery will take him right back to Caravaggio himself and the reasons he had to flee Rome, all those centuries before...