Under attack from outside, the nation is gripped by fear of an enemy whose destructive power and reach remain a terrifying unknown.

Authorities launch a dragnet and arrest dozens of suspects. A handful of lawyers step forward to represent the accused - and they are vilified, sometimes by lawyers within their own firms.

It all sounds a bit like the bitter debate that has swirled around the pro bono representation of hundreds of accused al-Qaeda operatives by lawyers from some of the nation's most prominent firms.

But a similar scenario played out decades earlier in the Julius and Ethel Rosenberg nuclear-spying case. Then, an obscure Philadelphia chemist named Harry Gold spent years passing nuclear secrets to the Soviets leaked to him by a German-born physicist working on the allies' crash program in New Mexico to develop an atomic bomb, the Manhattan Project.

Public revulsion at Gold's crime, coupled with fear of the Soviets, who only months earlier in September of 1949 had detonated their first atomic bomb, made representing Gold a hazardous career choice.

Yet it was a chance two Philadelphia lawyers of blue-blood lineage and impeccable conservative credentials decided to take.

Shortly after Gold's arrest at his home in Northeast Philadelphia, the two lawyers with the firm of Pepper Hamilton L.L.P. stepped forward. John D.M. Hamilton was a former chairman of the Republican National Committee and favorite lawyer of Philadelphia's powerful Pew family; Augustus Ballard came from a lustrous Philadelphia legal family. His grandfather had founded Ballard Spahr L.L.P.

Their work quite possibly saved Gold's life; it most certainly changed their careers forever.

"These two lawyers are the only heroes in the whole saga," says historian and author Allen Hornblum, who details Gold's life and espionage activities in a new book: The Invisible Harry Gold, published by Yale University Press. "They stuck with him for 22 years."

That Gold was central to the Soviet goal of pilfering U.S. nuclear technology is little in doubt. He was the Soviet's only courier to physicist Klaus Fuchs, part of the British team that helped Americans design nuclear bombs dropped on Hiroshima and Nagasaki.

Every few months, Gold would schedule a vacation from his job as a chemist at Philadelphia General Hospital, and travel to Santa Fe, N.M., among other places, where he would meet Fuchs and pick up detailed drawings and instructions about the nation's nascent atomic bomb program, and then deliver them to a Soviet handler in New York.

Julius Rosenberg, a well-documented member of the same Soviet network, and his wife, whose role in the spying operation was somewhat less certain, were executed in 1953, and are better known than Gold.

But Gold's work for the Soviets probably was much more central to the success of their atomic program, if only because Fuchs had given him nearly complete design details of the American bomb.

There are many fascinating aspects in Hornblum's book - the wrenching descriptions of Depression-era Philadelphia, in which Gold was raised, the late-night walks through the streets of Center City by Gold and his Soviet handler, and clandestine spy meetings at the Franklin Institute.

But perhaps the most striking is the decision of Hamilton, a quintessential establishment figure, to take up Gold's defense.

Hamilton had been raised in prosperous circumstances in Topeka, Kan., and went to prep school at Phillips Andover Academy in Massachusetts before graduating from Northwestern University. He forged a career as a lawyer and state legislator in Kansas and played a key role in Alf Landon's 1936 presidential campaign, when Landon made him national GOP chair.

Hamilton also was a highly successful commercial lawyer, and a favorite of the Pew family, of the Sun Oil fortune, who brought him to Philadelphia.

He was intrigued by Gold, an intelligent, hardworking lover of opera, literature, and the Philadelphia Phillies, whose main character flaw, apart from the stunning dishonesty of his spying career, was his inability to say no - to coworkers and friends asking for loans, to employers urging him to work harder, to the Soviet operatives he eventually connected with.

Just as important to Hamilton and Ballard was the principle that an accused criminal, no matter how heinous the offense, was entitled to a defense.

Judging from the way the Gold case played out, civil rights protections and courtroom procedures at the time seemed lax. Federal Judge Patrick McGranery disclosed during one hearing that he'd had ex parte communications with FBI Director J. Edgar Hoover about the case, an acknowledgment that today would cause a criminal case to implode.

Hornblum writes that the FBI, after wearing Gold down with repeated visits and searches of his home in May 1950, got him to admit his espionage activities. They then holed up with Gold for days in a hotel room, where they continued to pump him for information.

Ballard and Hamilton realized early on that the case against Gold was weak, if only because he had been questioned for days without a lawyer. The case itself was based almost entirely on Gold's abject and fulsome confession.

But corroborating testimony from Fuchs was not possible because the British government had imprisoned Fuchs in the United Kingdom for giving up British nuke secrets to the Soviets. It was not clear that the Brits would allow him to come to the United States to testify.

Meantime, the Americans, in a major breakthrough, had deciphered Soviet cables showing that Gold had been one of their operatives.

Yet, use of that information in court would compromise the Americans' own counterintelligence.

If Gold retracted his confession, it was game over for the government. That would have placed Hamilton and Ballard in the delicate position of potentially winning the release of a detested enemy spy.

And that simply would not have gone over well at the Merion Cricket Club.

But it wasn't going to play out that way. Gold made a full confession.

Gold was sentenced to 30 years in federal prison, and was released after serving 16. He died in August of 1972, during heart surgery, having spent the final years of his life as a chemist at John F. Kennedy Hospital.

Ballard, who died two years ago, and Hamilton, who passed away in 1973, both went on at different times to chair Pepper Hamilton and were revered at the firm. They remained as Gold's lawyers for the rest of his life, never receiving a dime.

Contact staff writer Chris Mondics at 215-854-5957 or cmondics@phillynews.com