Such Men Are Dangerous — Lawrence Block

Once such man is Paul Kavanagh, an ex-Green Beret with nothing but time on his hands … until he gets an offer to steal a shipment of tactical nuclear weapons from the U.S. government … and finds himself a partner, George Dattner, who has the cold eyes of a trained killer.
Each of these men alone is dangerous. But anyone who tries to stop them together is guaranteed not to come out of it alive!