Work Is Murder

Dave wakes up after a vivid nightmare of having killed his boss, goes to work feeling uneasy, and things just get worse from there. We find out that his boss is dead, having suffered a heart attack, supposedly; and then we encounter both the bosses young daughter and Dave's odd work mates to make him feel even more guilt-ridden. By the end of the long day he is seeing things and talking to ghosts instead of just talking to himself. But then...