The original version of Fritz Lang's fantastic science fiction film Metropolis was first seen in Berlin in 1927. Shortly after, Paramount recut the film to (over)simplify the plot. From then on, it was thought that at least 1/4 of the whole film ended up on the editing room floor where it was swept into the dustbin of history. Recently though, much of the lost footage was rediscovered. According to ZEITmagazin, several of the rediscovered scenes are essential to the film's plot. The magazine has the story about how the missing reels ended up in the private collection of a film critic in the late 1920s or so, and eventually came to light again. From ZEITmagazin (poster image from Wikipedia):
Among the footage that has now been discovered, according to the unanimous opinion of the three experts that ZEITmagazin asked to appraise the pictures, there are several scenes which are essential in order to understand the film: The role played by the actor Fritz Rasp in the film for instance, can finally be understood. Other scenes, such as for instance the saving of the children from the worker’s underworld, are considerably more dramatic…The rediscovered material is in need of restoration after 80 years; the pictures are scratched, but clearly recognizable. Martin Koerber, the restorer of the hitherto longest known version of “Metropolis”, who also examined the footage, said to ZEITmagazin: “No matter how bad the condition of the material may be, the original intention of the film, including all of its minor characters and subplots, is now once again tangible for the normal viewer. The rhythm of the film has been restored.”
Lang's Metropolis rediscovered (ZEITmagazine, thanks COOP!)