Romeo has a premonition of Juliet's demise in the original play, however in the movie there is an absence of such a premonitionin the last scene with Romeo and Juliet on stage in the play, Juliet wakes to find Romeo next to her, dead. In the movie, this ending scene was changed to show Juliet wake up right before Romeo drinks the poison. She is too out of it to realize what is going on, and Romeo's attention is gotten right after he drinks the poison, when he turns to find Juliet alive
