It may come back into play at the climax of the story, but sometimes the MacGuffin is actually forgotten by the end of the story. Usually the MacGuffin is the central focus of the film in the first act, and then declines in importance as the struggles and motivations of characters play out. The MacGuffin is common in films, especially thrillers. Common examples are money, victory, glory, survival, a source of power, a potential threat, a mysterious but highly desired item or object, or simply something that is entirely unexplained. In fact, the specific nature of the MacGuffin may be ambiguous, undefined, generic, left open to interpretation or otherwise completely unimportant to the plot. A MacGuffin, therefore, functions merely as 'a plot element that catches the viewers' attention or drives the plot of a work of fiction'. In fiction, a MacGuffin (sometimes McGuffin or maguffin) is a plot device in the form of some goal, desired object, or other motivator that the protagonist (and sometimes the antagonist) is willing to do and sacrifice almost anything to pursue, often with little or no narrative explanation as to why it is considered so desirable. For the block cipher, see MacGuffin (cipher).