The film's central conceit of an innocent man being mistaken for a fictional spy was suggested to Hitchcock in the early 1950s by journalist Otis L. Guernsey, Jr.. In turn, Guernsey had been inspired by stories he'd heard of fictional spies the Allied Forces had invented during World War II in order to fool the Germans. In a subsequent letter to Hitchcock, dated October 1957, he explained:
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.
In order to proceed with the pre-production of North by Northwest, Hitchcock secured the rights to the story from Guernsey for $10,000.
In order to help divert attention away from Kendall, the Agency has created a fictional secret agent named George Kaplan and Vandamm is led to believe that Kaplan might thwart his attempts to smuggle state secrets out of the country. The Agency stays one step ahead of Vandamm by moving the fictional Kaplan from hotel to hotel, giving the illusion that Kaplan is hot on his trail.
Whilst Kaplan is apparently booked into the Plaza Hotel in New York City, two of Vandamm's henchmen — Valerian and Licht — mistake Madison Avenue advertising executive Roger O. Thornhill for the US agent and kidnap him. They take him to meet Vandamm, who has temporarily taken over the house of United Nations diplomat Lester Townsend. Thornhill's pleas that he is not Kaplan only seem to make Vandamm more certain that he has finally captured the illusive spy and he orders his execution.
After the henchmen fail to kill him in a staged car crash, Thornhill gains entry into Kaplan's unoccupied hotel room at the Plaza where he discovers that none of the hotel staff know what Kaplan looks like. As the henchmen close in once again, Thornhill flees to the United Nations to confront Townsend. As a confused Thornhill talks to the real Lester Townsend — who knows nothing about Vandamm or the misuse of his house — one of the henchmen throws a knife into the diplomat's back and Thornhill is framed for the murder.
Thornhill goes on the run from the police and telephones Kaplan at the Plaza only to be told he has checked out and has booked into a hotel in Chicago — in fact, Kendall had already alerted the Agency that Vandamm was heading to his hideout in South Dakota, via Chicago. Convinced that finding Kaplan is his only chance to prove his innocence, Thornhill boards the next Chicago-bound 20th Century Limited from Grand Central Terminal. On board, he is shielded from the pursuing police by Eve Kendall, who is travelling with Vandamm on the same train.
In Chicago, Thornhill survives a further attempt on his life and confronts Vandamm at an auction house before he is arrested for causing a disturbance. The police take Thornhill to meet The Professor, a spymaster who works for the Agency. Increasingly concerned that Thornhill is jeopardising their entire operation and is risking exposing Kendall, he explains that Kaplan doesn't exist and that Kendall is in fact working for the Agency. The Professor then persuades Thornhill to protect Kendall by having him act as Kaplan in order for her to pretend to kill him in front of Vandamm in a public place — the cafeteria at Mount Rushmore.
With Kendall's loyalty proven and the troublesome Kaplan dead, Vandamm finally feels he is safe enough to spirit the reel of microfilm, which he collected at the auction in Chicago, out of the United States.
Other Uses of the Name
- Film critic Robin Wood used the pseudonym "George Kaplan" for his 1972 article "Alfred Hitchcock: Lost in the Wood", published in Film Comment. Wood then replied to his article using yet another pseudonym!
- In the 1991 film Hudson Hawk, James Coburn plays a character named "George Kaplan". Unlike in North by Northwest, this Kaplan does die when his car goes over the edge of a cliff!
- The 2011 "Enemy on the Hill" episode from season 9 of NCIS included a contract killer named "George Kaplan".