The Alexander Litvinenko murder by radiation in London is mysterious -- and important. Has Russia entirely left the Western orbit, reverting to its old Soviet era, Stalinist practices? Is Vladimir Putin, approaching the end of his two terms in office and thinking of a new career, interested in being seen worldwide as having blood on his hands? 

Or something else is afoot? I have met Mr. Putin four times in the last three years. He is tough and smart, and perhaps ruthless, but he is not stupid. Does he understand the murders may make him look bloodthirsty and make Russia appear barbaric? 

And if he did not order these killings, they still make Russia look out-of-control, while Mr. Putin looks like he lost control. Are his secret police taking people out on his orders, or is he being framed by his own people? And if so, why? 

Thus, the poisoning in London of Mr. Litvinenko and murder of journalist Anna Politkovskaya, a fierce Putin opponent, on the Russian president's birthday, are mysteries of great importance for the West -- and Russia. They need to be solved, and the sooner the better. Decisionmakers in Great Britain, the U.S. and elsewhere eagerly await for answers. 

No question, Mr. Litvinenko had a murky past. A Federal Security Service (FSB) colonel who worked with Mr. Putin when he headed the service in the 1990s, Mr. Litvinenko later accused his former colleagues of planning to murder his patron, Boris Berezovsky. 

Mr. Putin partly owed his rise to Mr. Berezovsky, a billionaire who was the in-house financier and eminence grise of President Boris Yeltsin's inner circle. However, after Mr. Putin took office, he marginalized Mr. Berezovsky and several other wealthy Yeltsin-era oligarchs. 

In 1999 Mr. Litvinenko accused Mr. Putin and his former FSB colleagues of blowing up apartment buildings in Moscow to justify the start of the Second Chechen war, when the bombings were blamed on Chechen terrorists. 

In 2000, Mr. Litvinenko fled Russia and settled in Great Britain, becoming a citizen this past October. Shortly before his death, Mr. Litvinenko accused Mr. Putin of ordering the murder of Mrs. Politkovskaya. The Soviet secret services had a tradition of sentencing defectors and traitors to death and executing them. However, this stopped with the Soviet Union's collapse. These days double agents receive long prison sentences. 

Moreover, Mr. Litvinenko was fired from the service and left the country as a civilian, and there were no rumors of trial in absentia, let along a death sentence. Something else triggered his death. 

According to the Times of London, Mr. Litvinenko recently visited one of the former owners of the Yukos oil company, who is hiding in Israel. Mr. Litvinenko reportedly gave him evidence of alleged illegal acts carried out in the takeover of Yukos by the Russian government. This evidence will be transferred to Scotland Yard as part of its investigation into Mr. Livinenko's poisoning. 

The Litvinenko and Politkovskaya murders make Mr. Putin and his Russia look truly horrible. Mr. Litvinenko is the latest in a long list of political murder victims. Since the 1990s, political and business murders have plagued postcommunist Russia. 

Journalists have been targeted as often as politicians and lead the list of victims. In 1995, Vlad Listyev, a popular TV host, was gunned down. Dmitry Kholodov, an investigative reporter looking into corruption in the Russian military, was blown to smithereens by a paratroop intelligence officer. 

My friend Galina Starovoitova, a democratic Duma deputy, was gunned down at the entrance to her home in St. Petersburg. I also knew Yuri Shchekochikhin, a liberal opposition editor of Novaya Gazeta, who is rumored to have been poisoned. Duma member Sergey Yushenkov, who, like Mr. Litvinenko, was an ally of exiled tycoon Boris Berezovsky, was mysteriously gunned down by a colleague. Last year, Paul Klebnikov, the Russian-American editor of Forbes Russia, was murdered, and this year, top banking regulator Andrey Kozlov, Politkovskaya, and Litvinenko were all killed. 

Russian secret service agents assassinated Zelimkhan Yandarbiev, former president of the self-proclaimed independent Chechen Republic in February 2004. Yandarbiev was in exile in Qatar at the time. 

In the past, the Soviet spy services "took care of" many political opponents, including Stalin's arch-enemy Leon Trotsky in 1940 and Stepan Bandera, leader of the anti-Soviet Organization of Ukrainian Nationalists (OUN), killed by the KGB in Germany in 1959. 

Recently, under Mr. Putin's orders the Russian Duma passed a law allowing Russian secret service to use force to fight terrorists abroad. This happened after four Russian diplomats were kidnapped and brutally murdered by jihadis in Baghdad. However, Mr. Litvinenko was a political opponent of the regime, not a terrorist. 

There are rumors in Moscow that an organization of ex-KGB officers, called Honor and Dignity, may be behind at least some of the recent murders, but that may be a red herring of plausible deniability floated in the Moscow River. Or if the story is true, it surely brings back the specter of the Weimar Republic, where ultranationalist and Nazi veteran groups killed communists and social democrats, such as the Foreign Minister Walter Rathenau, clearing the path for the Nazi takeover.

It is also possible the murders are linked to the power struggle afoot in Moscow between siloviki -- the "men of power," including many in the FSB and presidential administration, who do not want a changing of the guard in the Kremlin, and the mostly nonuniformed Putin associates from St. Petersburg around Vice Premier Dmitry Medvedev, current heir apparent to the presidency.
    Whatever the motives, Russia is too important to ignore these killings. The sinister secret staring us in the face refuses to go away. We need the truth.

Ariel Cohen  is senior research fellow at the Heritage Foundation and the author of "Kazakhstan: Energy Cooperation with Russia -Oil, Gas and Beyond" (BMG Publishers, London, 2006).