Keith Moon's final night out was as a guest of Paul McCartney at the preview of the film The Buddy Holly Story on the 7 September 1978. After dining with Paul and Linda McCartney, Moon and his girlfriend, Annette Walter-Lax, left the party early and returned to a flat on loan from Harry Nilsson in Curzon Place, London. He died in his sleep at the age of 32, having overdosed on Chlormethiazole, medication taken as part of a program to wean him off alcohol. When the police investigated the cause of his death they determined that there were about 32 pills in his system. Some of the pills were undissolved.
http://en.wikipedia.org/wiki/Keith_Moon#Death