And then he was almost completely forgotten.

Erickson possessed the rarest trifecta in World War II espionage: he was important, even receiving the Medal of Freedom for his work. He was brave. And he was American. I became obsessed with finding out the truth about his life.

But I quickly learned that Erickson was unlike anyone I’d ever written about. He had secrets that were multi-dimensional, folded inward on each other.

He'd lied about his age, for starters. He was a full seven years younger than he claimed to be. And after months of research, I found he hadn't been an intelligence officer in World War I after all. In fact, he'd been a student at Cornell, pledging Beta Theta Pi and romancing co-eds while men died at the Western Front. The first lie had opened up a gap in his biography, so Erickson had simply created a past as a spy for himself.

Other Erickson myths had been created by Hollywood and the publishing industry. In 1958, the author Alexander Klein wrote The Counterfeit Traitor about Erickson's life, and four years later Paramount released a hit film. William Holden played the spy.

I expected that the film would be, like “Argo,” bad with the facts. And it was. The thrilling escape from Germany had never happened, among many other things. But the book, too, turned out to be dodgy. That time Erickson killed a Gestapo agent in a Berlin phone booth? Klein had ginned up that one, and Erickson played along.

I began to feel that Erickson didn’t want me to find out the truth about his life. Writing about him was a caper in itself, like hunting a brilliant mole.

My next discovery was, however, altogether different. Erickson hadn't begun working for the OSS in 1939, it turned out, out of patriotism and anti-Nazi feeling. It had been 1942. And he wasn’t pretending to be a Nazi collaborator as part of his cover. He'd actually been one all along. Erickson’s business ledgers for 1939 alone showed he'd earned millions in oil deals with the Third Reich, a fact he tried to hide for decades. And he'd kept on making money until he'd been placed on the Allied black-list and his brother in America had been forced to disown him.

Erickson wasn’t a Nazi, by any stretch. But he didn’t mind making money off them. Becoming a spy, it turned out, was an act of atonement.

I felt my heart sink. This wasn't the discovery -- or the Erickson -- I wanted. 1942 was four years after Kristallnacht, three years after the invasion of Poland. No one could remain confused about Hitler in 1942.

I tried to place the new information in context. I went to Stockholm and talked with Sweden’s pre-eminent WWII historian, who explained that trading with Germany was considered a matter of national survival – if Sweden didn't give Hitler the raw materials he demanded, invasion would likely have followed. And American businesses like Standard Oil were doing business with the Third Reich right up until 1941, weren’t they?