The Descent
Oftentimes countries receive different versions of a film, not just because of language barriers, but because of cultural differences. British test audiences enjoyed the bleak ending where Sarah escapes, only to wake up back in the cave, realizing she had only dreamt of escape as the crawlers close in on her. American audiences, however, did not enjoy that ending. So, production simply cut out the last 30 seconds revealing it was just a dream.
Watch the alternate ending HERE.