By Richard Jerome
March 18, 1996 12:00 PM

The modest row house blends seamlessly into its sleepy block in southwest Cambridge, England, just as its resident, retired Cambridge University physicist Theodore Alvin Hall, long ago absorbed himself into the old college town. Born in Far Rockaway, N.Y., the Harvard-educated Hall, 70, enjoyed a distinguished scientific career before coming here. As a brilliant young physicist during World War II, he was recruited for the Manhattan Project at Los Alamos, N.Mex., and helped build the first atom bomb. In later years, he was a preeminent researcher in the field of electron microscopy. Now frail and gaunt and racked with Parkinson’s disease and kidney cancer, Hall rarely ventures out, and he and his wife, Joan, a retired instructor in Russian and Italian, seldom entertain. “I always thought he was a bit of a hermit,” says an elderly woman who lives across Owlstone Road from Hall. “He’s not the sort to say hello.”

Imagine the surprise of the aging Cambridge scientist from New York City when, on Feb. 11, he came to the door and found Michael Dobbs, a British-born Washington Post reporter, who had arrived unannounced. That wasn’t the half of it. Dobbs, 45, had come to ask if Dr. Hall was one of the most important—and mysterious—spies of the century: “Mlad,” the Soviet agent who leaked secrets to Moscow 50 years ago.

“He might have started yelling and screaming at me,” says Dobbs, a former Post Moscow correspondent now working in Washington. “But he was perfectly polite and very civil.” More to the point, Hall neither confirmed nor denied being Mlad. “These events, or supposed events, happened 50 years ago,” he said. “If they are made public, there will be a certain amount of interest, but it will soon die down.”

That hypothesis will now be put to the test. On March 5, the U.S. National Security Agency released documentation confirming that Theodore Hall was, in fact, Mlad. Known as the Venona papers, the documents are a body of World War II-vintage Soviet cables intercepted by U.S. intelligence and deciphered over the next 30 years.

As a spy, Hall may rank with Klaus Fuchs—a Los Alamos physicist considered the most significant Soviet A-bomb spy of them all—whom the British sentenced to 14 years in prison in 1950. Certainly Mlad far outstripped Julius and Ethel Rosenberg, the American couple executed for treason in 1953.

“The Rosenbergs had some crappy drawing of a lens,” says Gary Kern, who recently coauthored a book with ex-KGB colonel Vladimir Chikov on Soviet nuclear espionage.

It was Kern who last year alerted Michael Dobbs to the Venona papers, which ultimately led the Post reporter to suspect Hall. At that time, well before the NSA’s March 5 revelations, several passages that indicated Mlad’s identity had been blacked out. Library of Congress historian John Haynes speculates that the U.S. knew Mlad’s identity but kept it hidden. Exposing the Venona information by prosecuting Hall, Haynes suggests, “would have compromised the code-breaking operation.”

Even so, Dobbs found parallels between Mlad and Hall that were “too great to be coincidences.” Most strikingly, Mlad was described as a Los Alamos physicist recently drafted into the U.S. Army; Hall was called to Army service in 1944 but stayed on to work at the Los Alamos laboratories.

A furrier’s son, the precocious Hall was only 18 then but already a cum laude Harvard graduate. After the war, he earned his Ph.D. at the University of Chicago and in 1947 married Joan Krakover, with whom he has three grown daughters. As early as 1950, the FBI was reportedly investigating Hall for espionage. But two years later the matter was dropped. That year, 1952, Hall accepted a job as an X-ray researcher at the Sloan-Kettering Center for Cancer Research in New York City. He moved on to Cambridge in 1962.

“He was very famous when he arrived,” says zoology professor William Foster, citing Hall’s work on the electron microscope. “There was a slightly sad air about him,” adds Peter Duncumb, a physicist who, like most of Hall’s colleagues, has expressed shock at the Mlad revelations. “Because he was so quiet, he never gave the impression of being a political animal.”

In a 1991 article, his close friend, the late zoologist Brij Gupta, noted Hall’s “almost self-effacing modesty” and scorn of pomp: “He loves to caricature the traditional use of the academic gown by acting as a Batman.”

Hall, it seemed, rarely discussed his early career. Roger Moreton, once a research associate, never even knew that Hall, later a nuclear disarmament activist, had served on the Manhattan Project. “I guess he was keen to forget that part of his life,” observes Moreton. “He must have been horrified with what was done with his work.”

All of which invites a troubling question. “He turned over the most powerful weapon of its time to Joseph Stalin,” notes Gary Kern. “That’s a pretty dumb thing to do. I’d like him to explain it to the world.”