Alfred Hitchcock historians and trivia-loving fans of North by Northwest may already know the story behind how the concept of the Cary Grant starring thriller came to be, but if you're not up to snuff on your Hitchcockian origins, it goes a little something like this: Hitchcock hired screenwriter Ernest Lehman to adapt a novel called The Wreck of the Mary Deare. After a few failed attempts, Lehman told Hitchcock he couldn't crack the novel, but instead of parting ways the now-friends decided to find out a way to work in an idea Hitchcock had long wanted to film; a chase across Mount Rushmore. They brainstormed over possible scenarios that could spark that chase, but eventually settled on the idea of a man who is mistakenly thought to be a spy.
The idea, however, was not their own. It was based on an idea that a journalist, Otis L. Guernesy, had told Hitchcock nine years prior about the real-life story of a few British intel officers during WWII who, out of boredom, created the identity of a fake masterspy for the Nazis to hunt down. They went back and forth about how to tailor the story to America and how to pin the spy identity on an unwilling party, but ultimately nothing came of it until a few years later when Guernesy wrote a letter to the director that essentially handed him free rights to his story.
From the letter:
"I suggested to you that this escapade might be built into a good movie melodrama in any one of a number of ways. The actual treatment we discussed at the time involved an ingenuous young American--probably a traveling salesman--who has the fake identity pinned on him by accident and finds that he cannot get rid of it. He is on the spot: the enemy is trying to capture and kill him. and his friends cannot help him because they cannot afford to have their ruse exposed.
However you plan to use the idea at this time, I hereby hand it over to you, blithely and with best wishes, with all rights and privileges, etc., etc., with no purpose of evasion or mental reservations, etc., etc., for such consideration as may have been discussed between my agent and yours, for all the good it may do you which I hope will be plenty."
Now stepping back a bit, it's hard to imagine that letter being written today. Imagine a journalist pitching an idea to a hot shot director during an interview. It's an idea he's always been infatuated with and would love to see said director turn it into a movie, and though said director doesn't immediately jump on it, it keeps tumbling around in his brain for the better part of a decade. Were that to happen in today's climate of copyright law where Hollywood is quick to lock down the legal rights to even the faintest of ideas, you can bet heavily that were the film to be made, it would be because the studio had paid outright for the concept.
However, that's not what happened with North by Northwest. After Guernesy freely (and officially) handed the rights to the script's framework to Hitchcock, Hitchcock turned around and paid Guernesy $10,000 for the idea despite no legal reason to do so. Ernest Lehman still has the sole writing credit, but it's nice to know that Hitchcock and co were unwilling to shaft the little guy, so to speak.