In the movie "Strangers on a Train", we see Guy entering Bruno's house at night, using the key and the map and carrying the gun, all of which Bruno had given him earlier. Then we know that he's just going to talk to Bruno's father about his son's madness and has no intention to kill him.
I simply don't get it! Why in the middle of the night? Why in the father's (supposed) bedroom and not anywhere else? Why while carrying a gun?