For Hollywood films, narrative momentum is the key ingredient. This means plot devices are an inevitability; Alfred Hitchcock coined the term "MacGuffin" to describe these devices, which are of vital importance to the characters but a passing care at best to the audience.
Per Hitchcock's definition, the MacGuffin itself isn't what's important, but how it drives the narrative and characters forward. This means that several films don't explain what the "MacGuffin" actually is, only that the characters want it.
10 The 39 Steps Has One Of Hitchcock's First MacGuffins
Given Hitchcock is the one who coined the term, it's fitting that even the early films of his pre-Hollywood era, made in his native Britain, contain such plot devices. One of the more nebulous examples is The 39 Steps—this title refers to the plot device; a conspiracy out to steal British military secrets.
However, nothing about the nature of this spy ring is divulged; to whom they owe their allegiance is unanswered even in the film's closing moments.
9 Bad Times At The El Royale Doesn't Reveal Who Is On The Film Reel
Bad Times At The El Royale follows a group of strangers who meet at the titular hotel in 1969. The El Royale, located on the California/Nevada border, has been a temporary home to many famous guests. Indeed, one of the MacGuffins is a film reel of one of those guests; the FBI seeks to silently recover it, for whatever's on the reel is incriminating for its subject.
The film doesn't reveal which historical figure appears in the footage. There are some clues; the time frame, that the person in question is dead, and their real-life proclivities could point to either John or Robert Kennedy, or perhaps Martin Luther King Jr. The answer, however, is for the viewer to decide.
8 Cast Away Doesn't Reveal What's In The Package
Robert Zemeckis' Cast Away features Tom Hanks as Chuck Noland, a White Collar FedEx worker whose mediocre existence ends when a plane crash strands him on a desert island. Left with not much company beyond volleyballs and miscellaneous FedEx packages, Chuck leaves one unopened—when he makes it back to civilization years later, he delivers it.
Since Chuck never opens the package, viewers never get to see its contents either. According to the filmmakers, however, there is an answer: two bottles of Salsa Verde. Clearly, sometimes mystery is for the best.
7 Fast & Furious 6 Mentions Its MacGuffin Once
The Fast & The Furious series has traversed through many genres during its 20-year lifespan. However, since 2013's Fast & Furious 6, the series has settled into the spy thriller mold. The aforementioned film sees Dominic Toretto's crew recruited to capture a mercenary team led by Owen Shaw (Luke Evans). Per Luke Hobbs (Dwayne Johnson), Shaw's crew is attempting to build a "Nightshade" device.
Much of the relevant exposition is only half-audible, but the MacGuffin is apparently some kind of EMP weapon. According to the director's commentary, Justin Lin only included this MacGuffin as a flimsy story hook and intentionally left it vague. Appropriately, the Nightshade device plays no role in the climax, not even as a "ticking clock" common in action movies of FF 6's ilk.
6 Kiss Me Deadly Is A Forebear Of This Phenomenon
Many unrevealed MacGuffins come in the form of briefcases or boxes. The beginning of this is Robert Aldrich's 1955 Kiss Me Deadly. A noir set under the shadow of the Cold War, the "Great Whatsit" at the center of the film's story seems to be nuclear in origin; Gaby Rodgers' character gets the misfortune of a fiery death when she opens it.
However, it's never precisely explained what it is, and whenever Mike Hammer (Ralph Meeker) attempts to learn more, he's obfuscated.
5 Mission Impossible III Doesn't Answer What The "Rabbit's Foot" Is
Considering JJ Abrams' famous "Mystery Box" TED Talk where he describes his approach to storytelling, it's no surprise one of his films appears on this list. Indeed, it's his debut—Mission Impossible III. The film's villain, Owen Davian (Philip Seymour Hoffman) seeks to acquire a device called the "Rabbit's Foot" for his arms-dealing business; he eventually blackmails Ethan Hunt (Tom Cruise) into stealing it for him.
While it appears onscreen, what the device is or does is never explicitly confirmed; the biggest hint is the "biohazard" label adorning it. However, this is one mystery box that didn't need to be opened for an entertaining film to result.
4 North By Northwest Has Secrets Kept Even From The Audience
Though made during his time in Hollywood, North By Northwest feels akin to Hitchcock's earlier British espionage thrillers. In many ways, from the globe-trotting to the villain hideout, it's also a prototype James Bond film. Unlike Bond, however, Roger Thornhill (Cary Grant) is totally out of his depth—he's a Madison Avenue advertising man mistaken by USSR agents for notorious (and, it turns out, non-existent) spy "George Kaplan."
In this case, the spies led by Vandamm (James Mason) plan to smuggle a microfilm reel containing "government secrets" to Russia. What those secrets are remains unrevealed.
3 Pulp Fiction Never Explains What's In The Briefcase
Pulp Fiction contains easily the most famous example of an "unrevealed" MacGuffin. Marcellus Wallace (Ving Rhames) may want his briefcase back, but why he does is anyone's guess. Whenever opened, the briefcase emits a golden glow, which if anything just furthers the mystery.
At one point in the scripting stage, the case contained diamonds. However, Tarantino decided this was too simple an answer—not helping was that his previous film, Reservoir Dogs, was about a diamond heist. Thus, Tarantino decided to leave the contents unrevealed, betting correctly that this was more tantalizing than any answer. The cherry-on-top that is the golden glow is a nod to Kiss Me Deadly, minus the immediate lethality.
2 Ronin Has Yet Another Mysterious Briefcase
Ronin is the penultimate film by the late John Frankenheimer. It's also the exact sort of stale beer, action-heavy spy thriller for which MacGuffins were made. In this case, the MacGuffin is yet another briefcase—specifically, one which the IRA wants and which Sam Regazolli (Robert De Niro) must keep out of their hands.
Audiences get no better look at this briefcase's contents than they did the ones in Pulp Fiction or Kiss Me Deadly.
1 Those Who Wish Me Dead Gives Only The Barest Hints
Since his transition from TV actor to screenwriter/director, Taylor Sheridan has specialized in movies which (a.) are bound to thrill suburban American dads and (b.) that seem more akin to films decades older than their contemporaries. His latest and most convoluted, Those Who Wish Me Dead, is no exception.
In one of the movie's multiple story threads, forensic accountant Owen Casserly (Jack Weber) makes some discoveries that put two hitmen (Aidan Gillen and Nicholas Hoult) on his trail. What Casserly discovered is just barely hinted at; like so many of these movies, what matters is the chase, not the object.