London's Better-Than-Bond Spy Story

News analysis by CBSNews.com's Tucker Reals

Poison, murder, mystery, espionage, dossiers (the Brits love dossiers), lots of clues, lots of possible motives, the only thing lacking is a lurid sex angle — sorry, I still haven't found that — yet.

So far, London police haven't called Litvinenko's death a murder. They will. Nobody doubts that the former Russian intelligence agent died of a huge dose of polonium-210, and I'm confident the autopsy set to begin Friday will confirm that.

Traces of the man-made isotope have turned up in at least a dozen spots across this capital city and in several aircraft.

This stuff isn't your everyday household cleaner.

They don't sell seaweed-polonium rolls at the Itsu sushi restaurant where Litvinenko dined the day he fell ill, and you can't get it at drug stores. He was poisoned.

So who done it? Here's a look at the suspects:

Vladimir Putin

Litvinenko himself blamed the very Russian security services from which he defected for his death, or at least a statement he supposedly wrote on his deathbed that was read immediately after his death did.

Motive: When he defected to England, the former spy took up a new life as a full-time Moscow/Kremlin critic. He was investigating the murder of veteran Russian journalist and fellow Kremlin critic Anna Politkovskya, and based on an e-mail given to him by an Italian contact (who I'll get to later), he was about to implicate Putin's henchmen in her shooting.

Opportunity: Getting a hold of some polonium and smuggling it into the U.K., then somehow getting it into Litvinenko is tricky. But Vladimir Putin runs a huge country with all the nuclear technology it could possibly need, lots of money, and a vast network of some of the best trained secret operatives in the world. The resources are there.

But did he do it? Our Moscow bureau chief tells me Litvinenko was little known in Russia before his death, and his opposition work was more a nuisance than a catastrophe for Putin.

Furthermore, being a legal U.K. resident, and given the pressure already brought upon the Kremlin by Politkovskya's murder, Putin had much more to lose in the way of international prestige through Litvinenko's murder than he did from Litvinenko's accusations.

But there is evidence, sort of. The day he got sick, the ex-spy met with two Russian men at a London hotel, one of whom, he told police, he didn't recognize. Could the man have been a Russian agent? Sure he could have.

Then there are the planes. Two aircraft that have recently flown routes between London and Moscow tested positive for traces of polonium-210 and another is grounded in Moscow awaiting tests. Police want to check out at least two more. But the planes also landed at hundred's of other airports before being parked.

And even if it is determined that the chemical was flown into London from Russia, it could easily have been at the request of someone elsewhere … or even an elaborate tactic to confuse investigators.

Boris Berezovsky

Litvinenko's new life in London was funded by another exiled Russian with fierce anti-Kremlin views: Boris Berezovsky.

The billionaire is often referred to as Litvinenko's mentor, and he made his central London office available to the former spy for phone calls and other practical visits. That office is one of the six locations where police found traces of polonium-210.

Motive: Berezovsky made his billions in the '90s when the Russian government privatized lots of industry. Like a handful of others, he bought in, and got very rich — earning himself the title "oligarch." Then the government charged him with fraud and tax evasion and he fled to London, a wanted man.

Berezovsky has long been loudly and publicly critical of Putin's leadership. But now there are rumblings that he may actually be trying to instigate a forced overthrow of the Kremlin — a concept he's mentioned before.

Former Russian premier Yegor Gaidar became violently ill at a conference in Ireland one day after Litvinenko died. He's recovering in a Moscow hospital and doctors have said he was, in fact, poisoned.

We don't know, but the symptoms — a rapid onset of vomiting and fainting — sure sound like a milder version of what Litvinenko described.

"The chain of deaths of ... Politkovskya, Litvinenko and Gaidar, would perfectly correspond to the interests and the vision of those people who are openly talking about a forceful, unconstitutional change of power in Russia as a possible option," said Anatoly Chubais, a top official under former President Boris Yeltsin who now heads the national electricity monopoly.

Chubais' remarks on Russian television didn't name names, but those "people" he referred to were very likely Berezovsky and his cohorts.

In short, Berezovsky could have killed his friend to make Putin look bad, real bad, and/or to instigate a revolution in Russia. Not very nice, but this is business we're talking about.

Opportunity: Money may not buy love, but will buy anything else, and polonium-210 is no exception. A quick online search and look at the blogs reveals that the radioactive poison may be available for as little as 70 bucks to whoever wants it.

Berezovsky has plenty of money. He could easily have acquired some polonium-210 and used his many contacts (remember — he was very well acquainted with Litvinenko, and surely has other spies and security operatives in his little black book) to poison his buddy.

But did he do it? Who knows, but lots of people very familiar with Russian politics and affairs consider him the prime suspect.

Berezovsky, I should now mention, has flatly denied any involvement in Litvinenko's death.

Mario Scaramella

On Nov. 1, just before getting sick, Litvinenko met Mario Scaramella at a sushi restaurant in London.

Scaramella, an Italian security expert, had called Litvinenko to request the meeting. He wanted to give the former spy a copy of an e-mail that allegedly showed both men's names on a hit-list for Russian agents that also included Politkovskya.

The Italian went back to Rome after their meeting, but returned to London for a chat with the police and to be tested for contamination with the deadly isotope.

It came out Friday that the Italian was being hospitalized after the health agency confirmed that another individual had tested positive for contamination with a "significant quantity" of polonium-210. It's Mr. Scaramella.

You'll note the lack of subheadings used above — that's because if Scaramella did have a reason to want Litvinenko dead, it eludes me.

Friday's development that he is poisoned with the same stuff only bolsters the doubt in my mind that he's the cluprit.

He surely knows a lot of people and could afford some polonium at 70 bucks a pop, but I have seen or read nothing suggesting he would have, or could have killed this man. If I'm proven wrong, please leave appropriate "I told you so" comments below.

The Story Ends?

The English have been investigating mysterious murders for a very long time. Think Scotland Yard, Sherlock Holmes… you get it.

This case is snowballing at an impressive pace, with leads branching off in multiple directions and a trail of polonium-210 there for the authorities to follow.

If anyone can solve this case, it may as well be the Brits.

That said, whoever killed Alexander Litvinenko was very good at their job, clearly didn't act impulsively, and didn't think they were going to end up getting caught.

Nobody has been able to say who was behind Politkovskya's murder yet. And a long list of other political dissidents — not just from Russia mind you — have been killed or "disappeared" without any conclusive blame being laid.

And that, I fear, is where this great murder mystery diverges from the path of a classic novel. There may never be an ending. The snowball may just keep rolling then melt, when this season of public interest makes way for the next.