The Whatsapp message appeared on his iPhone: photos of an ancient Mesopotamian vase worth $250,000, part of a highly valued set, is waiting to be extracted.

The recipient, Amr Al Azm, replied that he was interested. How to proceed? A message from a different account followed. The vase could be smuggled through Lebanon.

Al Azm, an anthropology professor in Ohio, was faking it, as he does when photos of looted antiquities are sent to him in the belief that he is a collector or dealer. He is a detective — self-appointed — hoping to save some of mankind's rarest and most vulnerable artifacts by tracking the burgeoning antiquities trade of Islamic State in Iraq and Syria.