Alfred Hitchcock and The MacGuffin Plot Device

Photo is the set from the movie Psycho. Photograph by Superchilum.

In the 1960 horror/suspense film Psycho, starring Anthony Perkins as the legendary Norman Bates, scream queen Janet Leigh makes a brief appearance as Marion Crane, a bored secretary in Arizona who steals $40,000 when her employer asks her to deposit the money in the bank for a customer. Instead of stopping at the bank, Crane takes the money and runs, headed for California in her car. Exhausted from a day of driving, she pulls to the side of the road to sleep, but a police officer wakes her up and becomes suspicious of her anxiety.
The tension is rising for the audience, as well. Crane trades her car in at a dealership and returns to the highway in a different vehicle, then she is caught in a sudden rainstorm and forced to find a motel. She chooses the Bates Motel because it is isolated from the highway traffic, which provides her with a false sense of security.
At this point, the audience is introduced to the star of the film, Anthony Perkins, the shy, insecure motel manager who lives with his mother in the Bates Mansion, the deteriorating house on the hill. Bates invites Crane to dinner at trathe mansion and Crane overhears Bates arguing with his mother who suspects Bates of being sexually atcted to Crane. At dinner, Crane suggests sending Mrs. Bates to an institution, which clearly upsets Norman.
Crane returns to her room and decides to return the money, making lists of how she can repay the money already spent. She then steps into the shower while Bates watches through a peephole. Next we see one of the most famous horror scenes in film history as the shadow of a woman is seen entering the bathroom. She repeatedly stabs Crane through the shower curtain. It is now clear that the mystery--the disappearance of Crane and the strange motel manager--are the focus of the film. The $40,000 is The MacGuffin.
What is The MacGuffin?
The MacGuffin was used in storytelling for years, but director Alfred Hitchcock was the man who made the use of this plot device, and its name, famous. The MacGuffin is something that motivates the characters to do almost anything as they pursue, protect, or control an object, person, or even a place, with little or no explanation as to why this object, person, or place, is important.
Alfred Hitchcock, who directed and produced Psycho, made the use of this plot device, and its name, famous. In Dick Cavett's 1972 interview with Alfred Hitchcock, Cavett asked Hitchcock to define The MacGuffin for the audience. According to Hitchcock: "It might be a Scottish name taken from a story about two men on a train. One man says, "What's that package up there in the baggage rack?" and the other answers, "Oh, that's a MacGuffin." The first one asks, "What's a MacGuffin?" "Well," the other man says, "it's an apparatus for trapping lions in the Scottish Highlands." The first man says, "But there are no lions in the Scottish Highlands." And the other one answers, "Well, then that's no MacGuffin!" So you see, a MacGuffin is nothing at all." 
Hitchcock's story may seem a bit vague, but his point is that The MacGuffin is not really important because it's a plot device. The package on the baggage rack builds tension, creates a mystery, it is a possible reason for suspense, but has nothing to do with the story of what is happening, or has happened, or is about to happen to the two men on the train.
In the 1959 mystery North by Northwest, also directed by Alfred Hitchcock, The MacGuffin is the mysterious "government secrets." In the 1964 mystery/drama Marnie, directed by Alfred Hitchcock and starring another famous scream queen, Tippi Hedren, paired up with Sean Connery of James Bond fame, The MacGuffin is the color red.
The Birds
In the 1963 horror thriller The Birds, The MacGuffin is a pair of love birds that Melanie Daniels, played by another famous scream queen Tippi Hedren, buys as a gift for Mitch Brenner's (Rod Taylor) younger sister. The presence of the birds in Bodega Bay seems to set off a series of attacks by birds of all species, and there are a few hints in the film to indicate the love birds are The MacGuffin, but the response of the residents to the presence of Melanie Daniels in the town could also indicate a second MacGuffin in the film as Melanie Daniels and the love birds arrived at the same time, which would make Daniels a MacGuffin. In the end, no one really knows why the birds attacked, but the attacks do seem to be a warning against the mistreatment of the environment, a theme explored more deeply in the film's sequel, The Birds II: Land's End. Some film reviewers have indicated that the reason for the attacks by the birds is The MacGuffin, but the bird attacks are an integral part of the plot and not a simple device to keep the plot moving. 
The Thomas Crown Affair
Although Hitchcock used The MacGuffin often in his films, it was not his invention. He was not the only writer, director, or publisher to use it in films past and present. In fact, both versions of The Thomas Crown Affair contain solid examples of the use of The MacGuffin. 
In the 1999 version of The Thomas Crown Affair starring Pierce Brosnan and Rene Russo, The MacGuffin is a painting: Monet's San Giorgio Maggiore at Dusk. In the 1969 version of The Thomas Crown Affair starring Steve McQueen and Faye Dunaway, The MacGuffin is $2.6 million dollars. The two films are essentially the same--bored millionaire plans or commits the perfect crime; sexy insurance investigator solves the mystery; the couple falls in love. In the 1969 version, Steve McQueen, who plays the millionaire, is not caught, but the lovers are sadly parted. In the 1999 version, Pierce Brosnan also gets away with the initial crime, but he returns the painting in the end and runs away with Rene Russo. The audience is left with the impression that the millionaire's temporary life of crime, and his life of boredom, have both ended, replaced by a new life with Russo.
So, what about the money and the painting? In the end, no one really cares. The money and the painting are plot devices used to move the story forward, but neither one is important because the story is about the romance between the millionaire and the investigator. The audience is lured into a high degree of sympathy for both the millionaire and the insurance investigator--two bored and lonely people--and they are so completely focused on this love affair between the couple that nothing else matters. The money, the painting, The MacGuffins, are now precisely what Hitchcock called them in the Dick Cavett interview. They are "nothing."