Yesterday's movie was the story of a guy who wakes up in the morning remembering an eerie, rather dark, dream—a nightmare of sorts where he killed a man.

At first, he feels reassured at being awake, telling himself it was just a dream, but he suddenly notices he's holding two objects in his hand (a key and a button) he recalls as being present in his dream. It goes without saying that from then on the dream will haunt him up to the point of calling in sick to work and paying a visit to his brother-in-law, who happens to be a cop.

The intermingling of dream and waking life is a common topic in literature and film, be it psychological or—even more likely—fantasy narratives. You have for instance Coleridge's poem about the flower you find yourself holding in your hand upon waking up, Zhuang Zhou's butterfly, and so on, a battery of related topics spanning along centuries and that can arouse feelings of gloom, bewilderment, or exultation.