We have unraveled the mystery of the century - who really killed John F. Kennedy? We have studied evidence that had been covered up, and we have interviewed witnesses who had been silent for 25 years. Here are the highlights:The Central Intelligence Agency dispatched assassins to Cuba in 1961 to kill Castro. The operation was so sensitive that only six people had knowledge of it.

The killers were hand picked for the CIA by Santo Trafficante, who had been the Mafia boss of the pre-Castro underworld in Havana. After six professional hit teams failed, the CIA reportedly learned that Trafficante had double-crossed them and had tipped off Castro. The CIA immediately cut the Mafia out of the conspiracy, but continued the operation.

Without Trafficante to alert him, Castro no longer knew when or where the CIA assassins would strike. So, in September 1963, he delivered a public warning that if the CIA continued its attempts to kill "Cuban leaders," then "American leaders will no longer be safe."

Participants in the plot on Castro's life claim that the Cuban ruler then enlisted Trafficante to turn the Mafia guns against President Kennedy. Trafficante allegedly got the blessing and backing of two other Mafia godfathers, Sam Giancana and Carlos Marcello, who had come to hate Kennedy bitterly for his crackdown on the mob.

For a crime of such magnitude, the Mafia would have needed someone to divert suspicion from themselves. They allegedly were led to Lee Harvey Oswald, a perfect fall guy. He was a political crackpot who once defected to Russia. Yet, he had also been a Marine Corps sharpshooter with an assassin's skills. To the public, he would look like a misfit who acted alone.

Two months after Castro's warning, President Kennedy was gunned down in Dallas. The Mafia scheme, our sources say, was to pin the assassination on Oswald, then eliminate him before he could incriminate any conspirators. But the police found Oswald first.

That made it all the more urgent for the Mafia to get rid of Oswald. But who would pull a gun in front of dozens of armed police and shoot their prize prisoner? Such a killer would have to be crazy, or under terrible pressure. The man who did it, Jack Ruby, was not crazy. Our sources say he was a small-time hood under Mafia pressure. He had no choice, one source said.

The CIA veteran who directed the abortive attempt to assassinate Castro, William Harvey, told his superiors that the operation had backfired against Kennedy. They were told the CIA had confirmed this from other sources.

In the mid-'70s, a congressional committee investigated the CIA's use of Mafia hit men to knock off Castro. Investigators started asking questions about the possibility that Castro used the Mafia to retaliate against Kennedy. Subpoenas were issued for Santo Trafficante, Sam Giancana and the mobster who worked with Harvey on the operation, Johnny Rosselli.

Trafficante fled to the Caribbean and hid out on his yacht, our sources say. But Giancana and Rosselli did not escape. Before they could say anything that might link Trafficante to the crime of the century, both mobsters were murdered - Giancana in 1975 and Roselli in 1976.

Police concluded from the available evidence - most of it inadmissible in court - that the two were hit by Trafficante.