Nadezhda von Meck
On one occasion they met one another by accident.  Nadezhda had invited Tchaikovsky to stay at her home.  This was a huge house in enormous grounds, so it was easy to arrange that they should not meet.  They agreed that they would not go out at the same time.  However, one day he came home late and she went out early.  She was in a horse carriage and he was walking.  When they saw one another they looked away quickly.