BONN, Germany -- It did not end the way cloak-and-dagger stories are supposed to, with briefcases exchanged on foggy bridges, or midnight dashes across nameless borders.
Instead, one of the most thrilling chapters in Cold War espionage closed with a German nursery rhyme sung by a lonely, drunken spy:
"All my little duckies, swimming on the pond . . . heads deep in water, tails to the sky."
The bizarre shortwave broadcast from East Germany to its legion of spies around the globe that evening last May 23 hid a sobering message.
The game -- their game -- was over.
And the skill with which they played it is only now coming to light.
Just over two months into unity, the Bonn government is finding to its amazement and embarrassment that all three West German intelligence agencies harbored double agents at high levels and that this rampant treachery for decades provided the East bloc a treasure trove of Western secrets.
Intelligence analysts say that the damage is impossible to assess, and defense attorneys for the alleged spies being arrested on an almost daily basis argue that German unification makes it all moot, anyway.
Virtually every niche of the West German civil service apparently had moles on the payroll of Communist East Germany's secret police, the Stasi, whose lust for information was so consuming that they even bugged the church confessionals of their own countrymen.
"We now figure they recruited 5,000 to 6,000 agents in West Germany. We thought they only had 3,000," said Peter Frisch, vice president of the country's internal security agency, the Federal Office for Protection of the Constitution.
The real surprise, though, was that so many West Germans turned traitor.
Recruitment techniques varied. During the late '70s and early '80s, for example, East Germany planted handsome young men in West Germany to woo unwed secretaries in ministries. At one point, the so-called "Romeo escapade" included four secretaries working in the office of the West German chancellor.
On other cases, West Germans, such as a senior counterintelligence official, Klaus Kuron, approached the East Germans and spied for money. Mr. Kuron doubled his income during the eight years he admittedly worked as a double agent for East Germany.
Still others spied for ideological reasons. A diplomat, Hagen Blau, told investigators that he had been an impassioned leftist since his student days in Berlin, where a friend who joined in the cafe debates confided to Blau that he was a Stasi member.
The "friend" waited two years before turning Blau, who was then embarking on his foreign service career. Blau would spend the next 30 years supplying the East Germans with West German documents and information concerning foreign policy, purportedly rebuffing all offers of payment until the very end.
A common language and culture, as well as West Germany's open-door policy for East German refugees, gave East Germany a unique advantage in espionage, intelligence experts say.
And although West Germany also had no language or cultural barriers to cross, the closed society and iron-fisted Communist rule made it far more difficult for West Germans to plant their own spies in the East, and far more dangerous for East Germans to turn traitor.
Meanwhile, in West Germany, the infiltration was so thorough, according to Mr. Frisch, that even the home telephones of at least one-third of his agency's 2,500 employees proved to be tapped by the East Germans.
"They also had the capability of listening in on all telephone traffic between West Berlin and East Germany," Mr. Frisch said, adding that about 25,000 telephones in West Germany could also be scanned by East German computers.
Federal prosecutors are now investigating hundreds of cases and have made more than 100 arrests so far, more than triple their usual caseload.
"It's going to take years to unravel," said an intelligence source speaking on condition of anonymity.
Intelligence officers say that the KGB no doubt reaped a gold mine of information over the decades from its loyal East German ally.
"The East Germans were just about the KGB's most reliable allies," said Chris Andrew, a Cambridge professor who wrote "KGB: The Inside Story."
He described the scale of East German spying on West Germany as "simply astonishing.
"They were pretty blatant about it," he added in a telephone interview. "East German radio would nightly broadcast messages for 'moles.' The head of East German foreign intelligence, Markus Wolf, had the reputation of being the ablest foreign intelligence chief."
Mr. Wolf, who has an arrest warrant pending against him in Germany, recently finished a book titled, "I'm No Spy," and is said to be in exile in Moscow, hoping for amnesty from Bonn.
He has hinted in interviews published by the German press that some of his ex-agents still remain unexposed in Bonn government circles.