I hadn't known till I read this post from Drew Mackie that the premise of the twist-denouement of Agatha Christie's The Mirror Crack'd from Side to Side was appropriated more or less exactly from an incident in the real life story of actress Gene Tierney. (Read the post for the details if you're not familiar with the plot.)
Unlike Marina Gregg, Tierney didn't murder her Heather Badcock, but rather simply walked away imperiously, providing a withering, rather heart-breaking quip after the fact.
I don't agree with Mackie's contention that Dame Agatha's use of this story in a breezy murder mystery makes her a "deplorable hack" or a "cheap, opportunistic, exploitative monster," though, except to the extent that all writers are cheap, opportunistic, exploitative, monstrous, etc. Which is obviously the case. You should watch what you say around novelists, since they will invariably cannibalize the best, least flattering bits and use them for their own purposes, and they won't always remember to say "can I use that?" before doing so. Anyway, using that anecdote as the linchpin of a murder mystery is very clever indeed, though I doubt many people, hearing that story, would have seen the potential so keenly. The book has never been one of my favorites, but I am impressed, and can't help liking it a little more now that I know a bit about how it was inspired.
added: reading a few of Mackie's "related" posts, I came across quite a few other such interesting stories accompanied by imputations of mean-spiritedness that I couldn't agree with, or fathom. Here's a post about the actress credited as Angela Dorian in the film Rosemary's Baby (in the role of Rosemary's laundry room friend Terri Gionoffrio.)
Mackie is disturbed by the fact that the script has Rosemary tell her she looks like Victoria Vetri, the actress, when in fact, Angela Dorian's real name is Victoria Vetri. There's a "meta" gag in there somewhere, somehow ("personally, I don't see the resemblance," she says) but I can't say it ever struck me as sinister in any way. As with Dame Agatha and Gene Tierney, I can't quite fathom Mackie's outrage over what he deems a "malicious wink" on (I presume) Polanski's part:
She achieved some fame as a sex symbol, but never became a household name — as Victoria Vetri or Angela Dorian.
Consequently, the joke now seems mean-spirited because not only is it unlikely that dumb ol’ Rosemary Woodhouse would have recognized her, but today hardly anyone else would either.
Roman Polanski said,"by the way, how do you look in dark hair and can you look Italian?" I said, "well, I am Italian." He said, "I'd like you to play the part of Terry Gionoffrio, Angela." I said, "Okay," and I played the part under Angela Dorian, my fictitious name. On the set one day he said, "Angela, we cannot use Anna Maria Alberghetti name. Can you think of an Italian name?" I said, "How'bout Victoria Vetri?" He said, "that's fantastic! What an imagination!" I said, "that's my real name." He said, "my God, why are you using that name of a sunken ship, the Andrea Doria?" I think Victoria Vetri has more of a - ah, what the hell, it's Italian.Roman Polanski's sins are well known, but let the record show that maliciously winking at Victoria Vetri by casting her as Terri Gionoffrio and including her real name in the dialogue of one of the greatest movies ever made is not among them.
I was, however, surprised to learn that Victoria Vetri, the actress, is currently in jail awaiting trial for shooting her husband. Now that's weird.