Accidental Overdose (Star Trek)

Dr. McCoy received an accidental overdose of cordrazine. It was a thousand times the normal amount. Dr. McCoy became delirious and paranoid. He fled from the bridge and beamed himself down to the planet. McCoy then jumped through the Guardian of Forever and changed history. The Guardian of Forever told Captain Kirk and the landing party that beamed down to get Dr. McCoy “Your vessel, your beginning, all that you knew, is gone!”