Herbie Hawkins is an odd character in Alfred Hitchcock’s Shadow of a Doubt. He is kind, but seems socially inept, wandering into the Newton’s house during dinner. He enjoys talking to Mr. Newton, but only on the subject of the perfect murder. The only real affect he has on the story is his alerting the Newton’s to female Charlie’s screams in the garage. However, Herbie is very important to one particular agenda of the movie: re-writing the script of the detective story.
Early in the film, after Uncle Charlie has arrived but before any talk of dead widows, Herb and Mr. Newton discuss detective fiction on the Newton’s front porch. Herb points to an unseen story and says “That little Frenchman beats them all. You can talk all you like about Sherlock Holmes.” This conversation, though seemingly unimportant, actually puts the film in a very specific context. The “little frenchmen” is, presumably, Hercule Poirot, Agatha Christie’s famous detective featured in dozens in novels and short stories. The stories of both Sherlock Holmes and Poirot were whodunits—formulaic mystery stories in which the killer was revealed at the end of the story after the astute detective unravels a series of clues. Usually the killer is then arrested or dies, and justice is served. These stories were massively popular in the time period leading up to Shadow of a Doubt, with the first movie adaptation of a Christie story coming in 1928 (IMDb). Following is a typical ending to one of these stories, from the BBC version of Christie’s Death in the Clouds, with David Suchet as Poirot:
In alluding to these concurrent stories, Hitchcock is not trying to mimic these whodunits, but instead subvert them. In the Christie’s stories, the killer is never revealed until the end; in Shadow of a Doubt, the killer is revealed in the middle, with definitive evidence coming when Charlie finds the newspaper article with the names of the widows and matching them to the inscription on the ring. In addition, most of the whodunits end with justice being served, whether through imprisonment or death of the murderer. Shadow of a Doubt, however, while killing off Uncle Charlie, does not feature the final revelation. Young Charlie keeps the murder between herself and detective Jack, a shade-of-gray moral choice that goes beyond the simple “the villain goes to jail” ethics of most mysteries. In addition, the film even goes so far as to mock these simple tales; Herb, who is constantly discussing the perfect murder, is entirely oblivious to Uncle Charlies attempted garage murder of Young Charlie.
This subverting—and mockery—of the typical mystery plot is one way in which Shadow of a Doubt is a film noir. Many of the later noir films are also liberated from the traditional detective plot. Double Indemnity, released the next year, begins with the revelation of the murderer. This movement away from the entertaining, Scooby-Doo unmasking allows the filmmakers to focus less on plot and more on character. Indeed, in Shadow of a Doubt, Charlie’s internal dilemma over whether to reveal her Uncle is far more thought provoking than the detective’s attempts to solve the crime. It allows for the complex psychological character studies that appear in many film noirs, and usually makes for a more engaging film.