Out on the diamond of green, especially in that excruciating moment of stillness and anticipation before the ball shoots from the pitcher’s hand, the man behind the plate can be the most elusive figure on the field.

He squats while others stand, his face hidden by a mask. From that vantage point, at the pointy tip of the field’s perfect geometry, he sees all, but is barely seen.

This was the ideal place for a man like Moe Berg, an eccentric and enigmatic figure from baseball’s yesteryear. Berg’s exploits on the field in the 1920s and 1930s for the Washington Senators and other teams would come to be overshadowed by his cunning as a wartime spy in the infancy of the Office of Strategic Services, the precursor of today’s Central Intelligence Agency. Berg’s life and even the inscrutable circumstances surrounding his death 49 years ago linger as ongoing mysteries, a melange of fact, myth and opaque clues.

To encounter Moe Berg’s story is to become entranced with it. He spoke as many as 12 languages, became a radio quiz-show sensation, extracted a key Italian aerodynamics expert from behind enemy lines during World War II, and was sent to suss out the Nazi bomb-development program and, if necessary, assassinate the German nuclear genius Werner Heisenberg.

For decades, authors, filmmakers, scriptwriters and spy buffs have obsessed over him. In the past two years, Berg’s remarkable saga has flickered onto movie house screens — first in last year’s feature film, “The Catcher Was a Spy,” based on Nicholas Dawidoff’s critically acclaimed book “The Catcher Was a Spy: The Mysterious Life of Moe Berg,” and now in a deeply researched documentary, “The Spy Behind Home Plate,” by the Washington-based filmmaker Aviva Kempner.

“Everyone’s trying to nail it,” Kempner, now 72, says.

Kempner, who is best known for her documentary about Hall-of-Famer Hank Greenberg and for her activism on behalf of D.C. statehood, is a relentless digger. She gathered too many nuggets to fit into a single film, and she shared one curiosity with The Washington Post that didn’t make it into her documentary.

The baseball record books list Berg, the son of Ukrainian immigrants, as being born on March 2, 1902. But Berg’s birth certificate lists another date: May 3, 1902. It gets stranger from there. Moe was only a nickname — his proper name was typically listed as Morris. But the birth certificate shows his actual first name as “Moses.”

“Another mystery!” Kempner says.

Elusive from the start

Berg, who was said to have a photographic memory, was practiced in deception from the beginning. When he was a kid, he assumed a fake name so that he could play baseball on a Christian league team — there were no Jewish teams at the time.

For all her sleuthing, Kempner was never able to figure out where Berg lived from 1932 to 1934 while he was playing for the Senators, the Washington major league team for nearly six decades. But she suspects he spent much of his time at the Mayflower Hotel, one of his favorite haunts.

Even assigning a start date to Berg’s tenure as a spy has become an elusive task. Some think he began his life in the shadows as early as 1934, when he traveled to Japan with an all-star baseball team that featured the greatest players of his day, including Babe Ruth and Lou Gehrig. In Tokyo, Berg donned a men’s kimono — a sartorial flourish included in the documentary — and walked to a hospital under the pretense of visiting the daughter of the U.S. ambassador to Japan, who had just given birth. Instead, he dumped the flowers he’d brought with him and made his way to the roof of the hospital, then the tallest building in the city. He pulled a Bell & Howell camera from beneath his kimono and — in defiance of Japanese orders that no photos or films should be made during the visit — made a panoramic film of the cityscape that later made its way to the U.S. military, possibly for use in bombing raids, according to the documentary.

Berg was recruited to join the nascent OSS by the larger-than-life figure William “Wild Bill” Donovan, the founder of the spy agency. Berg was eventually handed the seemingly impossible task of finding Antonio Ferri, an Italian aerodynamics expert who had gone into hiding and had been privy to the secret workings of German scientists connected to the Nazi nuclear program. Berg found him and — because the former ballplayer spoke passable Italian — helped translate a cache of hidden documents.

But his scariest wartime ad­ven­ture required Berg’s special talent for fading into the background, like the masked catcher he’d once been. He traveled to neutral Switzerland, posing as a student, to hear a lecture by Heisenberg, the German nuclear scientist. His mission was to assess Heisenberg’s progress, and to kill him if it appeared he was getting close to developing the bomb.

Ever resourceful, Berg managed to take a walk with Heisenberg after a dinner party, a stroll in which he concluded the scientist still had a long way to go in developing the bomb — and therefore he passed up an ideal opportunity to kill him. In the feature film, there’s a shootout during the walk. Kempner doesn’t believe it occurred.

The feature film strongly suggests that Berg was bisexual. Dawidoff’s book says there’s no evidence to support that but briefly cites some rumors and speculation. Kempner also found no evidence, and points to his longtime relationship with a woman who was a piano instructor, and to interviews with former teammates who described Berg as “a ladies’ man” and a “womanizer,” albeit a classy one.

“I think that’s the Hollywood version,” Kempner says. “I’m trying to be very diplomatic. Facts can be more exciting.”

In a New York Times interview last year, Robert Rodat — who adapted Dawidoff’s book for “The Catcher Was a Spy” film — said: “The standards of veracity I applied in the movie were different.”

Neil Goldstein, a filmmaker who directed interviews with more than a dozen of Berg’s former OSS colleagues and baseball teammates years ago for a film that was never produced, said not one of them “even hinted” that he was bisexual.

“Why does this gossip remain a topic?” said Goldstein, whose interview footage is included in the documentary.

After the war, Berg spent time living in New Jersey with his brother, Sam, a physician, and later with his sister, Ethel. He never married, and he was a frequent presence in libraries, where he indulged his varied interests, and at major league ballparks, where he had been given a lifetime pass. He was awarded a presidential Medal of Freedom in 1945 but refused to accept it. He never explained why, adding another layer to his mystique.

Berg died in 1972 at the age of 70 after a fall at his home. His sister gave his remains to a rabbi and asked that they be scattered on Mount Scopus in Israel.

Kempner has unearthed letters from Sam Berg, first wondering whether the remains were ever actually scattered, then later puzzling over stories he’d been told by a rabbi about his brother’s remains possibly ending up in someone’s backyard in Jerusalem. He wanted his brother’s remains returned to the United States, since Moe Berg was never particularly religious. But that request was complicated by the fact that no one could tell him the exact location of the ashes.

It appears, according to Kempner, that Sam Berg never found his brother.