June 1943. Many Germans—some of them high-ranking officers—believe the tides of war have turned against them.

Increased activity suggests there may be truth to whispers heard by Office of Strategic Services spies: that the Nazis are extorting Jews outside Germany to buy their relatives’ freedom from extermination camps, then smuggling the ransom in Operation Phoenix to fund safe havens in Argentina, Brazil, and Paraguay for senior Nazi officials when Germany falls.

With so much money and more at stake, lives are, too, and it’s up to USMC Major Cletus Frade—the top OSS spook in “neutral” Argentina—to find out.

That is, before the ruthless Nazis order his murder...