Ok, I'll try to keep it short and sweet and cut right to the point. If you had foreknowledge of a negative event or events in someone's life, and you were in a position to warn said person, should you? Knowing full well that by doing so you are altering whatever fate/destiny/plans (divine or otherwise) are in place for that person in the hope that things will work out for the best? For example, you're reading a book or watching a movie and a character you like and/or sympathize with is going to be killed. If you had the ability, should you warn that character and save their life knowing that it was their death that led to the fundamental development and/or success of the protagonists?

I realize this is an old, old argument but I can't help but wonder anyway. Also, I am aware of the concept of "predetermined destiny" but for the purposes of this musing I am choosing to go with the concept of "free will".