I was about 23 at the time and went with this very old friend of mine (now) to a black tie New Year dinner at freinds of his house - complete withan Elizibethan gallery.......
After dinner there was a "young adult" version of Murder in the Dark - an excellent excuse to target a potentially attractive partner into a dark corner or cupboard for a kiss and a grope.....
It was about 1.15 - the parents came home and were surprised to find the house in darkness and, supposedly, everybody gone home.
The mother came in through the front door and the first thing she knew where a pair of hands coming around her neck from the "Murderer" (chosen by selecting the Q. of Spades from a pack of cards).
She survived and laughed about it for many years before her eventual demise - but it could have given a lot of folk a heart attack