Screenplay by Ernest Tidyman
Adapted from the book The French Connection: A True Account of Cops, Narcotics, and Conspiracy by Robin Moore
Two detectives notice a suspicious man surrounded by known underworld figures at a club one night and decide to investigate him. After many long days and nights of surveillance, they uncover that he is connected not only to the Italian mafia, but also to some mysterious Frenchmen who are highly suspected of smuggling heroin into the country.
This book does a great job of seeming true to life, but the result is that most of it is incredibly boring. All of the stakeouts and following people around do mostly pay off in the end, but they're rather tedious to wade through. The book effectively conveys how much endurance and perseverance was required of all the officers and FBI agents involved in this operation, but if it had been directly transported to the screen as is, it would probably be the most unwatchable movie of all time. But thankfully that's not what happened.
The movie doesn't seem to be at all burdened with remaining true to what actually happened. In fact, it doesn't own that it's based on a true story at all; at the end of the credits, there's even the familiar disclaimer about all events depicted being fictitious. This is already a significant departure from the book, which calls itself "a true account" in the title. All of the characters' names are changed (although the nicknames do remain the same), and most of the scenes in the film either aren't in the book at all, or are so altered as to be almost unrecognizable. Pretty much the only consistent scene is when the main detective, "Popeye" (Eddie Egan in the book, Jimmy Doyle in the movie) is following one of the Frenchman who has gotten on a train, then gets off, then back on, then off and on again. Popeye stays with him for most of that, but misses the last time he gets back on, and as the train passes him, the Frenchman smiles and gives him a little wave. That part is almost exactly the same in both versions. But for almost everything else, while some of the basic plot points are consistent, most of the details were completely changed. The movie is also way more exciting than the book; there's this whole intense part when one of the bad guys (who I'm not even sure existed in the book) hijacks a train and Popeye drives like a maniac through traffic to keep up with him, none of which was in the book. And the climax of the movie is about 50 times as intense as the climax of the book.
I can obviously see why the movie was changed to become more dramatic, but I'm not sure why it was so eager to distance itself from the source material, especially since the real detectives Eddie Egan and Sonny Grosso were credited as technical consultants and even made cameo appearances in the film. Maybe in some ways the movie was actually more accurate than the book? Or perhaps the film was more like how the detectives wished things had happened? Regardless, the movie is definitely more interesting than the book, so if you only want to experience one version of this story, I'd recommend the film.
The next book I'm reading for this project was the source material for two Best Adapted Screenplay Winners. Even though there's a different one in between them, I've decided not to read the book twice, although based on the first chapter it's almost infinitely more interesting than the last book I read. So stay tuned for The Godfather, based on the novel by Mario Puzo, then The Exorcist, followed by The Godfather Part II.