The main character does some Mental Time Travel to travel back into the past and save his girlfriend from being molested by her father. He does so by threatening him. What makes this scene so awesome is that during that time, he is in the body of his ten-year-old self and proceeds to talk down a man several times stronger and older than him.
He tops that in the director's cut. He finally realizes what the problem is, and solves it. He is, himself, the problem. Every time he travels through time, things get worse for someone. So he goes back to the womb and strangles himself with his own umbilical cord, leaving everyone else (including his parents, including his previously "insane" father) with a perfectly happy life. To top that? He was his mother's third stillbirth in this fashion.
Close, but not quite. His father still went insane in the same fashion as before - after Evan committed suicide in utero, and with his father already committed at this point, his mother remarries to a nice normal guy who doesn't have the ability of mental time-travel. The daughter that they raise therefore will also never develop the time-travel ability (as it was genetically inherited from Evan's paternal line) and so everyone is happy.