Before being cast as Elizabeth Grainger in The Virginian Sara Lane appeared in a William Castle film that has since become a cult classic. I Saw What You Did (1965) was the influence for the 1997 film I Saw What You Did Last Summer starring Jennifer Love Hewitt, Freddie Prinze Jr. and Sarah Michelle Gellar.
Sara (Sarah) Lane was cast a teenager, who along with her friend and younger sister, is involved in a series of prank phone calls. Their message “I saw what you did, and I know who you are” soon has deadly consequences.
The Virginian Weblog 
Actually I believe Sir Arthur Conan Doyle was the originator of this gag.
It featured in a Sherlock Holmes story.
Legend has it prior to the story he sent a letter to six friends “Flee Now All is Discovered” and some of those friends presumably had dark secrets!!
I wasn’t aware of this Michael. Thanks for mentioning it. It’s a cruel prank to play on someone but makes for an interesting idea for a story.
With friends like “Conan Doyle” Who needs enemies?