James Earl Ray, a drifter and ex-convict, shot and killed the Rev. Dr. Martin Luther King Jr. with a single bullet here on an April evening in 1968. That is the official story, the reason Mr. Ray spent the last three decades of his life in prison. Everybody knows it. But not everybody accepts it. Almost as soon as Dr. King was cut down -- and even more so after Mr. Ray recanted his guilty plea -- conspiracy theories abounded. Some said the assassin was an army sniper. Mr. Ray insisted he had been framed by a man named Raul, hired by the C.I.A. There was even a report that one of Dr. King's entourage had helped to kill him. Now ... the conspiracy theories have stirred to life again at the National Civil Rights Museum, in the former Lorraine Motel where Dr. King was shot. The museum recently opened an exhibit in a new $11 million wing primarily to document the assassination and the mystery that still surrounds it, at least in some people's minds. On display are 200 pieces of evidence, freshly unsealed from police archives. The gun. The 30.06-caliber bullet tweezed out of Dr. King's body. A fake passport and guidebook to Rhodesia found on Mr. Ray, curious artifacts for an unemployed ex-convict supposedly working solo. Questions are stamped on the wall, in bold letters. Did Ray have help? Did someone else do it? Was the Memphis Police Department part of the conspiracy?" The King family believes that Mr. Ray, who died of liver disease in 1998, was not the killer. Dexter King, Dr. King's son, visited Mr. Ray on his deathbed. The government killed my father, Dexter King told him, not you. Mr. Ray's family said they were finally getting the vindication they deserved.