Late in the afternoon, a former Russian intelligence officer goes to have tea in a London hotel.

He's meeting two old colleagues who have flown in from Moscow.

Not long afterwards, he becomes ill and is rushed to the hospital.

While there, he vomits uncontrollably.

He suffers excruciating cramps and loses body strength.

The result of a mysterious poison that had invaded his body and which baffles the doctors.

Less than three weeks later, the former Russian agent is dead.

The victim of a political assassination that the British government concludes was likely

ordered by the president of Russia, Vladimir Putin.

This may sound like the story of Sergei Skripal, the ex-Russia spy, who, as we speak,

is in critical condition in a hospital along with his daughter.

After what the British government believes was an attempted assassination,

a poisoning by a military-grade nerve agent that was authorized by Putin himself.

But it's actually about an event that took place nearly 12 years earlier,

the murder of Alexander Lithuanyenko.

Lithuanyenko was a defector and a whistleblower who fled Russia and took up residence in London,

dedicating himself to exposing what he believed was the corruption and brutality of Putin's regime.

What really happened to Lithuanyenko and why?

What did the British government and the US government do about it or not do about it at the time?

And what does this tell us about what needs to be done now in the wake of another assassination

attempt by the Kremlin? We'll explore those questions with somebody uniquely positioned to answer

them. Marina Lithuanyenko, the widow of Alexander Lithuanyenko, on today's buried treasure.

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