Other mistake: Once Dr. Trent enters the bedroom where Mrs. Loren is lying down "dead", they begin talking. Trent says "At first I couldn't get Nora to protect herself with a gun." There is no scene in the movie where he tries to convince her to use the gun, Lance is responsible for that. (01:02:25)
Suggested correction: After Annabelle Loren is found hanging under suspicious circumstances, both Lance Schroeder and David Trent advise all the other guests to stay in their rooms with their guns and shoot any intruders.
Just before he leaves for the meeting, Lance tells Nora, "If you have to, you use it." Nora was not at the meeting to hear what was said, so ultimately, it was Lance who got Nora to protect herself with the gun.
There's an important mistake in your version of Dr. Trent's quote. What Trent actually says is, "At first I couldn't get Nora to want to protect herself with a gun." He's not saying that he personally advised her to protect herself; he's saying that he, through his various scary tricks, had failed to scare Nora into arming herself. Trent's immediate next lines are: "But after you appeared at the window, everything began to work just as we planned. You were wonderful, just the touch that finally drove her into complete hysteria." We know that David Trent and Annabelle Loren were behind a number of staged scares (such as the witch in the basement, the attack on Lance, Annabelle's hanging, etc) intended to push Nora toward hysteria, setting her up, of course, to kill Mr. Loren "by accident," thereby committing the perfect crime.
Other mistake: When Lance leaves Nora to go have a meeting with the remaining people in the house and they accuse Loren of murder, his room is locked from the inside but when he returns he opens the door without any trouble.
Other mistake: In the beginning the "host" tells the guests that if they don't survive the $10,000 due them for staying the night will be paid to their heirs. A short time later he says that the entire $50,000 pot will be split among the guests who are still alive at the end of the night.
