Even seminal spy novelist John le Carré would have been hard put to craft such an inscrutable web of shadowy figures and murky alliances.
As Scotland Yard expands to Moscow its investigation of ex-KGB agent Alexander Litvinenko's poisoning, the "whodunit" theories now implicate just about every possible player:
•Enemies – or friends – of President Vladimir Putin
•Mr. Putin himself
•Russia's secret services
•The St. Petersburg mafia
•Mr. Litvinenko's friend, Boris Berezovsky, and even Litvinenko himself.
But another theory gathering momentum in Russia is that Litvinenko's highly public demise – taken with the October murder of Kremlin critic Anna Politkovskaya – are byproducts of intense jockeying for power ahead of Putin's departure in 2008.
"Putin has not yet made his plans clear over who will be his successor or what the process will be," says Andrei Ryabov, an expert with the Gorbachev Foundation, a Moscow think tank run by the former Soviet leader. "In the absence of clarity, the competitive groups may be beginning to act on their own, to reshape the political field to suit their own needs. It must be stressed that Russia is not a European-style democracy, where political struggle is limited by laws and constitutions."
Who benefits from Litvinenko's death?
One suggestion is that "enemies of Putin" in the hard-line silovik Kremlin faction, composed of members of the secret services, may be trying to drive a wedge between Russia and the West to fuel nationalist sentiment at home and improve chances for one of their number to become the next president.
"Politkovskaya and Litvinenko's murders reflect an internal struggle within the Russian elite," says Boris Kagarlitsky, director of the independent Institute of Globalization Problems in Moscow. "Some groupings are very interested in aggravating the situation, because the more tensions rise, the more Putin becomes dependent upon them."
Most Russian experts doubt any personal involvement by Putin in the alleged assassinations, but agree that the political consequences – domestic and global – can't help but fall at his doorstep. Indeed, some suggest, they may have been deliberately designed to do just that. Ms. Politkovskaya was shot on Putin's birthday, and just days before a crucial Russia-European Union summit meeting. Litvinenko's spectacular death-by-radiation in London last month came on the eve of another key European conference attended by Putin. "Everything has been going so well for the Kremlin, economically and politically, so why would Putin want to disrupt that?" asks Alexei Mukhin, director of the independent Center for Political Information in Moscow.
Another theory here is that "friends of Putin" are deliberately implicating him in the murders in order to convince him not to quit at all – since, out of power, he might not be safe from prosecution – and to grant himself a third term of office by amending the Constitution.
Polonium-210 – extremely unstable, fissiparous, and dangerous to those meddling with it – may be an apt metaphor for Putin's Kremlin and its turbulent inner politics. Over nearly seven years in power, Putin has built a traditionally Russian top-down system of power in whose workings he, personally, is the indispensible component. Yet Putin has announced that he will resign, as the country's 1993 Constitution prescribes, when his second term expires.
"This is the source of great uncertainty within the system, and it will increase as 2008 grows closer," says Masha Lipman, an analyst with the Carnegie Center in Moscow. "When you have a system that's hinged totally on one figure, any change is fraught with destabilization."
Some Kremlin experts here say the murderers will be found among the back-biting Russian-émigré community that Litvinenko inhabited, where intrigues and conspiracies allegedly abound. In particular, they point to exiled anti- Kremlin tycoon Boris Berezovsky, whom they accuse of trying to destabilize Russia in a possible bid to overthrow the Kremlin leadership in the troubled run-up to 2008. Russia's chief prosecutor, Yury Chaika, told journalists Monday that evidence implicating Mr. Berezovsky will be handed over when British investigators visit Moscow this week to pursue leads in the Litvinenko case.
"The version about Berezovsky's involvement finds further confirmation," former chief of the FSB security service Nikolai Kovalyov told the official RIA-Novosti news agency. "The ultimate goal of the operation could have been further building-up of KGB-phobia [in the West], to claim that Russia is ruled by members of the secret services."
Monday, lawyers for another former security officer – now in prison in central Russia – appealed to the British to collect testimony as soon as possible from Mikhail Trepashkin, saying he had key evidence and that his life was in danger.
In a letter from prison, Mr. Trepashkin, who was jailed for revealing state secrets, said he had warned Litvinenko several years ago about a government death squad that intended to kill Putin opponents.
Meanwhile, the pro-Kremlin daily Izvestia explored four theories of Litvinenko's death in an article last week, most involving Berezovsky.
First was the suggestion that Litvinenko may have been dealing in illicit nuclear materials, perhaps on Berezovsky's behalf, and was accidentally poisoned by his own contraband. The second, which casts Litvinenko as a hero, cites alleged evidence that Berezovsky may have been building a nuclear bomb for Chechen terrorists, using a polonium triggering device. In this version, Litvinenko swallowed the polonium "as his final service to his Motherland." In the third scenario, Litvinenko may have been planning to betray Berezovsky, and was killed by his erstwhile patron. "Think about where the first traces of polonium were found [in Berezovsky's office]," it said.
Izvestia's final theory, and the only one the newspaper attempted to debunk, is that Russian special services may have killed the turncoat Litvinenko in revenge for his defection six years ago. "But Litvinenko was a pawn.... There was no reason for Moscow to get involved in an international scandal [over him]," it argued.
British media have reported that the St. Petersburg mafia may have put out a hit on Litvinenko. Mario Scaramella, who helped Italy's parliament investigate cold war-era Soviet espionage, said he met Litvinenko at a London sushi bar on the day he is thought to have been poisoned. "We know very well who are the enemies of Litvinenko. The work we did for years was to underline the links among Russian mafia and some high-level corrupt officers in the Russian government," Mr. Scaramella told BBC radio.
Scaramella said that he showed Litvinenko e-mails warning that their lives may be in danger. The threat came from organized criminals in St. Petersburg, he said.
Regardless of who may have killed the Kremlin's vocal opponents – Politkovskaya and Litvinenko – the damage to Putin and Russia's fragile political stability may already have been done. "The atmosphere of lawlessness is undermining the unspoken rules that have kept Russia's elite more or less unified during the Putin years," says Mr. Ryabov. "Public faith in rule of law has been shaken. Any kind of political activity is starting to look very dangerous."
In order to obtain a large enough dose of polonium-210 to kill someone – as was allegedly done in Alexander Litvinenko's case – it would have to be manufactured by bombarding the metal bismuth with a stream of neutrons, say experts. The best way of doing this is in a channel-type nuclear reactor – common only in Russia, Britain, and Canada.
Russia produces about 8 grams of polonium-210 monthly, says its Atomic Energy Agency head, Sergei Kiriyenko. The entire output, produced at one plant in the Urals, is exported to the US for use in the paint and printing industries.
"The control in Russia is very strict," Mr. Kiriyenko insists. "We have only one producer, and it is transported under special conditions."
Polonium-210's alpha rays are weak, blocked by a few sheets of paper. In order to be deadly, a fairly large quantity would have to be ingested. But some Russian scientists say the choice of polonium as a weapon is logical.
"It easily diffuses," which means it can be used in aerosol form, says Nikolai Chechenin, deputy director of the Skobeltsyn Nuclear Physics Institute in Moscow. "Besides being radioactive, it is also a poison. So it has a double effect," he says.
Russian scientists say the Soviet Union experimented with polonium in a 1950s scheme to build a radiological bomb, but abandoned the effort due to the substance's very short half-life of 138 days.
• Information from the wire services was used in this report.