The Devouring - James R. Benn

Billy and Kaz are sent to neutral Switzerland to investigate the murder of a Swiss banking official with ties to the Office of Strategic Services (OSS). The US and Swiss governments are about to embark on diplomatic discussions and the OSS wants their involvement in the murder cleared up. The plans go wrong from the beginning when Billy and Kaz crash-land in France. Once they make it across the border, they find that the Swiss banks are openly laundering gold harvested from concentration camps, and that those who are profiting will do anything to protect their wealth and hide their secrets.