50 years ago, Karen Silkwood got in her car alone.

She'd agreed to deliver sensitive documents to a New York Times reporter.

She never made it. And those documents she was reportedly carrying were never found.

Do you think somebody killed her?

There's no question in my mind. If someone killed her

that night, I think they were trying to stop her in order to get the documents. I'm Mike Becher. I've

covered the world for network TV and returned home to Oklahoma to investigate the one story

I can't get out of my mind. And I'm Bob Sands.

I've been covering this liquid story since I read the wire copy on the air in Oklahoma City

the night that Karen died in that car crash.

Bluntly stated she was spying on her employer,

gathering evidence her union wanted to document charges of safety violations at the

Kermagee Corporation's nuclear plan.

For years, we've run down leads.

And in 1994, 20 years after Karen Silkwood's death, a friend gave me a secret tape for safekeeping.

An Oklahoma Highway Patrolman had launched his own risky investigation

behind the thin blue line.

I'm becoming increasingly concerned about the security at the FBI office, and that,

as I was told in beginning, I might be in danger.

I got the tape on one condition. No one else could hear it until the people named in it were dead.

That time has come.

We also found a trove of private investigator's tapes in a storage locker and tracked down

...