Plot hole: Darby goes to great pains to get out of the country, to where no one will know where she is but Grantham. But upon reaching her "secret" destination, a van pulls up to the plane and a man gets out and hands them an envelope with a copy of the front page of the Washington Hearld with their breaking story and both their names as by-lines. That couldn't happen unless other people besides Grantham and the pilots knew her destination.
Plot hole: Just after Rita rescues Jeff, Diane's grave is seen close to where Jeff was buried alive. Even though Diane's been dead for several years, her make-shift grave site looks like it was freshly dug. There are no fallen leaves or other debris on top, no new vegetation (moss, grass, weeds, etc.) of any type growing on it, nor has the mound of dirt settled, shifted, or been affected by the weather.
Plot hole: In the scene in the hotel, David sees the victim's head on the floor after the killer left. Later when David is in a hospital bed he is watching TV and the reporter claims that all the heads were in Judd's car. The killer would have had to have gone back into the hotel room to get the head of that victim after David saw it. She would have put it in her bag right away if she was saving them all. The bag was even left behind. (01:12:30 - 01:25:00)