The United States and Russia swapped 14 spies with precision, but one piece of the puzzle remains: The alleged spy who disappeared after posting bail in Cyprus.
Did he flee on his own? Get away with help from the Russians? Trick local residents into unwittingly aiding an escape? Meet some other fate?
The public doesn't even know his true name.
The alleged paymaster of the Russian spy ring was arrested June 29 in Cyprus on an Interpol warrant while trying to board a flight to Budapest, Hungary, two days after his 10 alleged co-conspirators were arrested in the United States. His companion, a beautiful younger woman, was allowed to fly out.
But the case dissolved into rumor-fueled confusion hours later when the suspect, who called himself Christopher Metsos, vanished after handing over a Canadian passport that claimed he was 54 and got released on bail. Police escorted him to a bank, where he took out $33,000 to pay the bail. Late that afternoon, he returned to a hotel and was never seen again.
No one apparently blanched that a man who had been acting like a budget tourist during his 13-day stay in Larnaca had such easy access to thousands in cash.
Metsos was "Defendant No. 1" in the criminal complaint that also named 10 Russian agents in the United States, all of whom were deported to Russia in exchange for four prisoners accused of spying for the West.
"If this man is what they say he was, he will have had some safe passage or probably turn up in Russia at some point," said Huw Dylan, a lecturer in intelligence at the Department of War Studies at King's College in London.
The brisk exchange of spies Friday at Vienna's airport was the culmination of an idea hatched more than a month ago at the White House, weeks before the Russian sleeper agents were even arrested June 27.
No evidence has emerged that events surrounding the Metsos mystery were linked to plans for a spy swap. American officials had said they were disappointed with his apparent escape. The Greek Cypriot government, in turn, said U.S. officials were slow to provide documents that would have made clear the importance of the suspect in their grasp.
The Interpol warrant, based on information from the United States, did not list espionage in the charges against him.
Cypriot authorities confiscated Metsos' laptop and several USB memory sticks at the airport and say they will turn them over to the United States if they contain data pertinent to the U.S. charges, which include money laundering and acting as an unregistered agent of a foreign government.
"We are in the process of finding out what is in the laptop," said police spokesman Michalis Katsounotos, who predicted an announcement about the computer next week. As for the spy swap, he said it had no impact on the Cypriot investigation.
"We are not interested in the political side," Katsounotos said.
If Metsos fled Cyprus, as is believed by local authorities after days of searching, the key question is to what extent, if any, he received assistance.
Canada said Metsos was using the identity of a dead Canadian boy, a fact that suggests he could have had access to other false documents enabling him to leave the country with ease.
Metsos is believed to have several aliases, and spoke English, Russian and Spanish, a security official said, speaking on condition of anonymity because he was not allowed to speak to the media.
The alleged spy was last seen in a hotel in downtown Larnaca, where he placed the "Do not disturb" sign on the doorknob. Hotel staff said he took a shower but did not sleep in the bed, had two suitcases that disappeared with him, and no one saw him leave.
Cyprus, an island in the eastern Mediterranean, is loaded with possible international exit routes.
Those include the airport on the edge of Larnaca; another airport in Paphos, a coastal town 90 minutes' drive to the west; Larnaca's marina or several other ports along the Greek Cypriot southern coast, home to thousands of private boats and ferries to Greece and other countries. One way to disappear would be to cross into the diplomatically isolated Turkish Cypriot north, whose airport only has direct air links with Turkey.
Unlike his alleged co-conspirators, Metsos did not live in the United States, according to the FBI. Instead, he allegedly delivered cash to agents there, meeting one many times in New York City and, on one occasion, burying a package believed to contain money north of the city that was retrieved by another agent two years later.
The criminal complaint against Metsos and the 10 Russian agents suggests he had a wry sense of humor. On March 31, 2002, at a meeting recorded and videotaped by the FBI, a Russian agent using the alias of Richard Murphy told Metsos that he was frustrated with his job.
"Well, I'm so happy I'm not your handler," Metsos allegedly said. The FBI believes he gave $40,000 to Murphy at that meeting.
Metsos flew into Cyprus from Vienna on June 17. Larnaca residents who met him described him as quiet and unremarkable, walking around the city in shorts with the woman with whom he planned to fly to Hungary. Hungarian police have told The Associated Press they have no information on her.
In the 1990s, Metsos once said he was Colombian, which backs up other reports that he speaks Spanish. He studied for a semester in 1994 at Norwich University in Northfield, Vermont, apparently giving them a false address and false phone number from Bogota.
It is not known where he has been living recently — but experts widely believe Russia is his final destination.
"He's got nowhere else to go," said Pavel Felgenhauer, a military analyst in Moscow. "Perhaps he's here already."
Associated Press writers Mansur Mirovalev in Moscow and Pablo Gorondi in Budapest, Hungary contributed to this report.