Early morning, April 4. Shot rings out in the Memphis sky. And although it actually happened at 6:01 p.m., despite what Bono sang, you pretty much know the rest – Dr. Martin Luther King Jr., the civil-rights leader, was dead, gunned down outside the Lorraine Motel.

That was 40 years ago this week. In honor of the anniversary, CNN will devote two hours Thursday night to retelling the assassination story and examining the conspiracy theories that suggest James Earl Ray didn’t act alone, if he acted at all.

The first hour-plus of Eyewitness to Murder turns out to be a thorough reminder/history lesson that recaps how civil-rights leader King and career criminal Ray’s paths collided. CNN rounds up pretty much everyone who’s still alive to be rounded up – King advisors including Andrew Young and John Lewis, Memphis police, Ray’s brother Jerry and his first lawyer, among others – to get their perspectives.

No one says anything especially earth-shattering, but it’s an impressive collection of interview subjects. And they recall some truly head-scratching details, including that black emergency personnel were vacated from the area near the Lorraine shortly before King was murdered. (No wonder some people see a cover-up.)

The last 45 minutes or so gets juicy as host Soledad O’Brien looks into what might have happened – if, that is, Ray wasn’t the one who pulled the trigger. The documentary more or less debunks the theories of Ray being framed, that there was a second gunman or that the owner of a nearby dive restaurant had a hand in the killing.

As you probably know, Ray pleaded guilty when he was finally captured in England two months later, but he almost instantly began recanting. He spent the rest of his life claiming he was set up.

I interviewed Ray by phone in 1992. He was serving his life sentence in Nashville, Tenn., at the time, and promoting his autobiography, Who Killed Martin Luther King? Ray claimed to have been at a Memphis gas station when King was murdered and said the man to blame most likely was a shadowy figure named Raoul. Ray couldn’t remember the name of the gas station or where it was, and no one ever stepped forward to provide him an alibi.

Ray went on to theorize that an FBI official named Cartha DeLoach masterminded a plot to kill King because of his opposition to the Vietnam War and set up Ray to be the fall guy. DeLoach’s name doesn’t’ come up in these two hours, so that’s one conspiracy theory still out there.

But clearly, the FBI hated King, whom agents described as “the most dangerous Negro leader in the country.” And as you’ll see here, that was one of the kinder things they said.

So maybe Ray was right. Maybe he was lying. More likely, we’ll never know. But good for CNN for asking the question again.