In my teens and twenties, I hung out with this core group of 4 or 5 girls. We always watched out for each other in general, but especially while out clubbing and/or drinking. At the end of the night, whoever was driving would call and let the phone ring just once to let us know she got home safely.
In 1992, one of my friends found out she had HIV and full-blown AIDS. Her health deteriorated quickly, and she died within a year of diagnosis. The day she died, as one of the other girls was sitting in her kitchen crying, the phone rang once. She got home safely.