Anna Navarro, special agent for the Justice Department, has been assigned to investigate the deaths of several eminent men, all advanced in age and all connected to a mysterious group called Sigma, founded in the last years of World War II. An accident brings her together with Ben Hartman, an American investment banker who is in Zurich investigating the death of his twin brother and finds himself the target of an assassination attempt. Who is Sigma, and why are some of its members being killed? More importantly, what grand project is in the works.